” African-Americans were slaves”
They ignorantly think being black meant being a slave and that wasn’t true.
Besides, blacks started slavery in America. Anthony Johnson, a black man, enslaved John Casor, a black man.
And, in addition to this, it was the courts that conferred enslavement onto Casor; granted, this was long before the Declaration of Independence, but I think that the founders were anticipating the repudiation of that travesty when they wrote the Declaration... it's too bad that the Constitution didn't abolish slavery, but the "3/5ths compromise" was indeed something that forestalled the civil war long enough for the Constitutional government to be adopted. (And it was our grave misfortune that the intervening time also had the institution intertwined into State's rights, leading to the conquest of the confederated states which, IMO, started the ball rolling on the tyrannical thought that the federal government is superior in every way to the States, turning the States into slaves of the federal government.)
Blacks started black slavery when they sold their African brothers to the Arab slave traders.
Blacks continued it in the south. There were thousands of blacks who were slave owners, more than 3,000 black slave owners in New Orleans alone.
Our country has perpetuated the problem with its welfare programs that result in the proliferation of the least motivated and the least productive.