And if you're going to bring up quotes by people who were viewed as forward thinking for their time from the 1850s opposing equality as an argument that white supremacy was too engrained in the American psyche for equality to have been achieved the Civil war changed a lot, including the hearts and minds of many; before the war John Brown was seen as a lunatic by the Union and by the end he was seen as a martyr.
And for anyone who's going to say "blacks are indebted to whites for freeing them", the Union Army was 10% black by the end of the war.
America was not built on slavery and the claim that it was is idiotically proposed by people who never studied history, don't know anything about the US and only wish to sow racial division and hate against the US.
Name one nation, one group in the entire world that did not have slavery of some kind. You can't. Now name the first nation to openly declare it as immoral? USA. Name the first nation to start banning it. USA. Name the only country in history to fight a war to end slavery when all other nations fought wars to create it. USA. Not only did we do this we did it a century before africa, the middle east, and asia would do it. We started it before Europe and if we take into account outside colonies, we where the first nation in general to out law slavery (as many european nations had banned slavery in their home nations by the time of the civil war, almost all of them had still allowed slavery in their colonies elsewhere).
So its not even an argument, we did more to end slavery then any other nations from an objective stand point, took part in slavery the least amount of time of any nation (about 80 years), we fought one of our bloodiest wars to end it (seconded only by WWII), and ended it while the rest of the world still practiced it. Their is no debate here.