Let me explain my dogmatic position before my historical one; only because the historical one is funnier. Dogmatically, Christianity is completely okay with slavery—an institution somewhat unique to blacks and American Indians in this particular country. Additionally, this is not one of those obscure customs of the Old Testament that many "Christians" like to pretend don't exist. Christ himself supports a slavery system in multiple teachings. Surely an American black person would be okay with a history of something that Jesus himself condoned. However, you might not yet be convinced.
Secondarily, I wish to use a similar Christian, albeit mostly evangelical, position that acceptance of Christ into your life and being born-again is the ONLY possible path to salvation. Lets play out a quick scenario. What if the Negro slavery system never existed in North America. The vast majority of black blood lines now living in the USA would still be in Africa instead. The majority of black people now living in America would instead live in Africa and would not know Christianity, therefore foregoing the possibility of salvation. Christians define the eternal life in heaven much more important than the struggles of mortal life. Therefore, American blacks that are Christian would have to be thankful (yes, thankful) that they were enslaved so that they were given the ability to learn about Jesus.
Is my position that black people should opt to not be Christian stupid, racist, mean, or even ignorant? Not in the least. Religion is for some reason the only thing that seems eternally exempt from criticism and logical thinking. I have been called all of these things but will never consider that it is religion itself that guides these illogical, idiotic doctrines into the minds of its followers. We cannot afford to be a society that believes these silly fairy tales anymore, it will destroy us. We have to be better than that.
Christianity: eternal suffering awaits those that dare to question God's unconditional love.