I figure it is way more complicated than he is making. Perhaps you should send him some books to read.
We probably were killing each other before Europeans invaded Africa and colonized it, and enslaved Africans To me, it is a moot point. Europeans slaughter each other. Asians slaughter each other. Killing of other humans is a human act, not really traceable to any particular ethnic or cultural group. If we all went with his theory, no one has the right to ever challenge poor treatment by some group who hates them. Jews, for example, who kill each other too, would have to shut up about the Holocaust. I hope he is aware that some Jews sold their own out during the Holocaust. I hope he is aware that Indigenous groups fought each other and this helped Europeans take over the land here.
Yet, the evil that has dominates our lives and has made it difficult for millions of African people to live a constructive existence is the racial caste system we live with called "white supremacy" as you say. Even if African people did everything exactly right, and were not so divisive, white supremacy is still right there. Black people (African people) are part of it. They are white supremacists at times. For survival. Because they are uneducated. Because they don't give a damn. It is going to take time to vanquish this shit that has happened. Pointing fingers at each other is not going to do it.