Only in Christian times and Christian countries has slavery become so twisted that in addition to denying the freedom of the slaves, it also denied the very humanity of the slaves. American slaveholders (and I presume British slaveholders, while slavery lasted in that country), salved their consciences by the elaborate fiction that black Africans were less than human. Thus, it was not only fair that they work for the white masters, but humane, because the white masters could save their proto-human souls by teaching them the rudiments of Christianity, and the beginnings of humanity.
If you look back at the publications of slave-holiding states in the United States and the Confederate States during the Civil War, you will see outright statements such as these. There are many depictions of the happiness of the slaves in their wretched quarters, singing and dancing in their rags, glad to be close to the masters. The verse in My Old Kentucky Home is rarely sung any more out of political correctness, but perhaps it is closer to re-writing history, in order to forget the ugliness of the whites. See this website that at least relates the re-writing of the song to edit out the inherent racisim of the song, written during slavery days.
The United States as it exists today, actually has done an amazing job of amalgamating a broad number of races, ethnic types and religions into a mostly stable and mostly friendly country. The biggest exception to this very optimistic statement is the Black community. While there is a large, stable Black middle class and some quite wealthy Black professionals, there is a permanent underclass of Blacks. They feel very hopeless, and are treated largely as if they don't matter and have no choice. I believe that most of the things that go on in the neighborhoods that are predominated by Blacks would never be tolerated in other neighborhoods. It only happens because it is a poor neighborhood, and mostly Black. And in America, that translates to THEM and Invisible.
This is at least in large part the terrible heritage of those slaveholders who had to salve their consciences. They could not simply own a human being as the Greeks, Romans, Egyptians did. They had to find an excuse to square it within their Christian religion. And they did this by perpetrating the monstrous sin on their slaves, of denying them, not only their freedom, and that of their families, but denying them their very humanity. And this echoes down through our history and culture. It poisons the slaves' great grandchildren, and it poisons all of us.
The decoration on this page is a medal made of the very famous anti-slavery image, with its slogan, "Am I not a man and a brother?" It comes from Steven Weisenberger's webpage at SMU.