Ah, but the owners had it between them in their social groups, and the slaves had their own version of it before they were taken from their homelands. It is not ours to say- nor was it the owners- what was civilized versus not merely because we were not or are not culturally sensitive.

The problem with this debate is that it's mixing two areas. You're trying to argue the historical aspects of the case against someone who is arguing the anthropological ones, and it's like fighting apples with oranges. You are not wrong historically, but you will offend and in their opinion, lose no matter how correct you are because you're not disproving the argument from their science. Do you see?