During the US civil war, the Democrats were the pro-slavery party and Republicans the anti-slavery party. The American South continued to be mostly Democrat into the 20th century - this changed when Reagan ran for president, as I recall. He inspired patriotism, so many yellow-dog Democrats switched.

The Dems also implemented welfare -- especially Johnson, but even before that -- and that destroyed the black American family, according to Thomas Sowell. It incentivized family breakup, resulting in fatherless boys and increased crime and drug addiction. These evils were not the legacy so much of slavery as of the welfare state - which continues to this day. If anyone should pay reparations, it's the Dems.

But black Americans vote for them en masse inexplicably, pulled in by their rhetoric. That's changing however. A lot of blacks voted for Trump in the past and I think more will do so this time around because of the economy. And they know BLM and identity politics is a scam. They see through the Democrat "welfare plantation" and how Lefties infantilize them. See the work of Larry Elder.

The Leftist predilection is to reduce the complexity of real life to a simplistic stereotyped narrative to make themselves feel morally superior. Life is more complicated than to say everyone is either an oppressor or oppressed. That binary can actually become the basis for real oppression, e.g., Stalin crushing the Kulaks because they were small property owners.

People forget that throughout all of human history, slavery was the norm, and it was not just in the American South. Nearly every society on Earth had slaves going back to prehistory. We are all the descendants of both slaves and slave owners if you go back far enough. The West abolished it in the 19th century but slavery is still going on worldwide illegally. I never hear Lefties who mentioned American slavery talk about or oppose the millions of real slaves today, who are of all colours, including white women from Eastern Europe forced into sex slavery (see the book The Natashas). They are just referring to America's past in order to disparage it, not because they really care about people who were enslaved.