Rawanda is nothing new - it just seems so because until recently such slaughters of blacks by blacks in Africa weren't considered worth reporting.

It was Africans, for the most part, who sold Africans into slavery (often through Arab middlemen). In many cases this was probably good for the slaves. If they didn't have monetary value they would probably have simply been slaughtered. They were generally just a byproduct of incessant tribal warfare.

True, the Arabs sometimes fetched their own supply, but their main method was "buy low, sell high".

We might be better off expunging all the African genes, but, alas, this would leave little, so it isn't going to be practical.