Part One: Resistance to Abolition
While it is true that the institution of slavery was a pillar of the economy in the southern United States for over two hundred years, I disagree with the unfair characterization of the South as full of bigots, wholeheartedly desirous to keep slavery in place forever. There were, however, a number of reasons why they refused to give it up right away.
First, the political balance of slave states versus free states had been established in the Constitution, when the census was set up to count enslaved blacks as two-thirds of a person, for the purpose of representation in the House of Congress. This caused the competition to declare whether new states coming into the Union would allow slavery or be designated as free. It was never clarified whether a free black would have any status for representation, or even given a vote in elections. The South was clearly hesitant to give suffrage to an uneducated class, when even white women were not so eligible as yet.
Secondly, the economic base in the South was primarily agricultural, and dependent on the labor of many hands, especially in cotton and tobacco. Meanwhile, the North was rapidly industrializing to make durable commodities, like steel and manufactured goods, and wage labor was becoming the norm. Expecting the South to pay wages to field workers would have put many farmers out of business, and there was little machinery available to lessen the workload.
Thirdly, slavery supported the southern way of life. The class structure of "genteel" society was based on the availability of servants, as it was in Britain. But in the South, it was cheaper to have slaves for house servants than to hire poor whites to do these jobs. A slave could be well trained to clean, cook and raise the children, and were taught, occasionally, to read and write. Some were even accorded preferential treatment, and given special perks, like a Bible or a musical instrument, which they could share with the others. And they could be expected to stay for life, while a white servant might leave at will, or for small cause.
Fourth, many municipal functions were often performed by slaves, such as lamplighters, street sweepers and trash collectors. It required considerable labor to keep streets clean when horses were the common mode of transport. Slaves were often utilized as labor for municipal construction projects. And occasionally, some small businesses were run by a slave who was entrusted by his master to manage a shop, in return for fair upkeep and kind treatment during the evening hours. In such cases, a slave might even be allowed to earn money to buy his freedom.
Not all blacks adapted this well to being slaves, however, and a recalcitrant attitude of disobedience was a quick way to earn a harsh punishment. The resultant horror stories that have been handed down serve to remind us of the indignities of the institution. It should never have gotten this bad. But not all whites regarded the "darkies" with proper kindness, as they should have, nor did all whites deserve the degree of respect that they demanded. It was often a matter of class and pride, with hired white overseers administering the abuse, or white owners lacking the conscience needed to finesse and control the situation.
So clearly, there was good reason to put an end to slavery in America, but it was going to be a long hard road. Everyone was going to have to adapt their lifestyles and social expectations. If there had been another way toward which they could have made a smooth transition, without flipping the economy on its head, or creating a new class distinction of an impoverished labor pool, the resistance to abolitionism might have been less.
Part Two: Causes of War
Slowly, there came some realization that slavery, while not forbidden in the Bible, was not, A) a preferred social structure, or B) practiced as the Bible dictated. And so, the institution would have been modified until it eventually faded away. The problem was the economy, and political entrenchment, and that was where they could not see any way to simply abandon slavery peremptorily. The culture relied on servants, and paying hired workers would have been a hardship, because of class issues, but that could have been worked out. Slavery could have been gradually phased out, as the conscientious awareness of how wrong owning human beings actually was would have grown. The Bible commanded that slaves were to be set free after seven years. Slaves were supposed to be an economic class, not the personal property of rich people.
Moreover, the institution of slavery in America was cruel and inhumane, and its practice was often abusive beyond measure or Christian conscience. There is no question about that, nor any argument for its justification. It had to end, sooner or later. Although some southern families did not mistreat their slaves, and even continued to employ and care for them after the war, the very idea that humans could be chattel property was repulsive. The Bible never intended that it should be that way. God freed the slaves from Egypt!
So the North wanted it to be an issue, and they wanted it dead and gone, NOW. They would not allow for a gradual transition, partly because the situation seemed to be getting ever more firmly entrenched, with the new slave states coming into the Union. Slavery could not be allowed to expand. So, Congress tried to increase the pressure on the southern states by imposing tariffs on interstate commerce, particularly on goods produced by slaves, but this was viewed as unfair. It soon was clear, with the election of Lincoln, that legislation to directly inhibit the trade and possession of slaves would be up for debate. The South had to secede, in order to protect and preserve their way of life... for however long it would last.
Thus, the reasons often given for why the Southern States seceded from the Union would include the perceived abuses of Congress treating them as a second class of states. The cry of "States' Rights" meant that the states should have been allowed to take their time to adapt and mitigate slavery until it passed out of necessity. And the tariffs were regarded as punitive, exacerbating the situation, and making the northern states richer at the cost of impoverishing the South. Moreover, no one knew how to ensure the functions of "democracy" when a new class of poor, uneducated blacks were to be given their freedom. Would literacy tests have to be imposed? Many whites could not read and write either. The process of adapting to a free society was going to take a long time. Even after the South lost the Civil War, it took over a century to come to terms with the changes that were imposed.
Part Three: Global Milieu
There is an often repeated accusation that white Americans were the perpetrators of the slave trade, going to Africa to steal black people away from their families and ship them off as slaves. This is simply not true. American slave traders NEVER stole any blacks from their homelands in Africa. They bought them from Muslim Arab slavers who captured them from conquered territories. The Arabs captured slaves for their own use, and for sale at the coast, and the slave traders, many of whom were British, bought them to sell in the Americas. At least, in the Americas, slaves were valuable for breeding, unlike in Muslim lands where the males would likely be castrated to insure they remained docile.
Slavery had been a fact of life from the very beginning of civilization. It was not an American invention. The condition of slaves had been deplorable in almost every case, because a slave typically had no rights, nor any legal recourse against abuse. A slave was chattel, basically livestock. Individually, a slave could achieve a reasonably secure and respected station, if he, or she, was liked by his/her owner and found favor, but that was not the usual expectation. A slave had no choice concerning the work he would be assigned to do, and some jobs could have a very short life expectancy under extremely harsh conditions, eg., a galley rower, a copper miner, or a road builder. And rebellious slaves were routinely killed or mutilated if they fought back or tried to escape.
The one exception, in ancient times, was in the lands owned by the Jews. Having once been slaves themselves in Egypt, they felt pity for slaves, and established some rights and conditions to delineate their position. In Israel, one could have become a slave usually for economic reasons, even voluntarily, due to extreme poverty or failed debt. This would have been a contractual agreement, involving monetary relief for the debt, and there was a limit to the time of servitude. According to the Law, a slave could only be kept for seven years, and one was expected to be given sufficient food, clothing and shelter. Of course, he/she could be commanded or disciplined, like a child, but if one suffered serious abuse or harm, which resulted in any disability or disfigurement, the contract would be ended. A slave would also be allowed to marry a partner of his/her choice, but still be obligated to fulfill the terms of both contracts. There was even a possibility that, if both the owner and slave agreed, the contract could be converted to a permanent one, making the owner responsible for the slave's welfare for life. The sign for this was for the slave's ear to be pierced, and given a gold earring. And even as a slave, anyone born a Jew was still considered a citizen of Israel. Presumably, a captive taken in war would be accorded similar consideration, if he/she converted to Judaism, or they could be exchanged for Jewish prisoners from the other side.
Clearly, American slavery did not conform to this Biblical pattern, and this was a cause for concern for those who regarded slavery as an evil, even a necessary one. But there were worse places to be a slave, particularly in Arab or Muslim lands. Still, the discomfort to the American national conscience was going to end the institution of slavery eventually, although no one had any ideas about how long it would take. Slavery had existed forever. But as history ran its course, it became the cause for a brutal, costly war.
And even while white Americans are still accused of prejudice, and blamed for the practice of slavery, in other parts of the world it still continues. The institution of slavery was not outlawed in Muslim countries until late in the 20th century, and enforcement is still a problem. Radical groups, like Boko Haram, continue to take captives and enslave the females who won't convert to Islam. And female slaves are used for sexual purposes, passed from hand to hand, according to the survivors. Why is this? Muhammad did this, and he was "a paragon of humanity" to be imitated by all Muslims. It would seem to be a contradiction to abolish a practice that your prophet enjoined on all his followers, right? But American blacks have gone over to Islam, just to spite the white Christians who could not end slavery fast enough, while Muslims have no qualms about continuing it. Only international pressure has been able to force them to make it illegal, and push the practice of slavery underground.
Part Four: Conclusions
The Civil War did not solve the basic social problems, nor any of the economic ones however, and the resulting resistance to integrating black people on equal terms with whites came from these problems remaining. There has always been class differentiation between rich and poor, but in theory this could be bridged by education. The sudden introduction of a class without voting rights created a system of oppression, once again institutionalizing both lesser education and lesser rights.
Jim Crow laws kept blacks as a bottom class, and stifled all efforts to rise from poverty and disrespect. The resulting hatred was then reflected on both sides as prejudice. It would be another hundred years before this deeply wrongful situation was addressed. The civil rights movement was slow in coming, but it did bear the long-awaited fruit. Legislation was passed to allow blacks to vote, and the Constitution was amended to give them equal rights. But prejudice dies hard, and children must be taught to overcome it by looking at an individual's character, rather than forever perpetuating racism. Only by treating others with the respect due to equals do we become equals.
Today, we have a golden opportunity to make things better, for ourselves and our children. As American children work hard daily to acquire a good education and improve their social class and status, and avoid such "acts of despair" as undermine society, they are being recognized as fully equal citizens with equal opportunities and futures. No class has ever gotten ahead without hard work, and privileges must be earned, before they are inherited. The adage asserting that "a black child has to work twice as hard as a white child to achieve the same results and recognition," is simply not true, but it is a continuing cause of more resentment and expectations for racism and oppression. We see what we expect to see, and such cold attitudes only make the situation worse.