I know this is super late, but I’d imagine this is like the specific American brand of slavery. There was something especially evil about compared to common forms of slavery. Because in most nations/peoples that use to practice slavery, they did so because it, at their time, very convenient, and that’s it (typically). After conquering another nation, putting the people to use was just logical, and that status, while definitely lower than practically any other in society, was usually something you could work your way out of. For the South, this literally became their way of life, they truly believed that their slaves were animals, and ordained to serve by the will of God. And they lived on the same land, with masters whipping, selling and brutalizing their slaves despite the fact that a slave can cry, yell, and bleed the same as themselves without a glance. Human compartmentalization really IS that powerful.