I don’t think this is correct. I think the show is much, much closer (minus the magic and demons and ghosts) to reality than most depictions of the era. Decent white people probably really were quite rare, in the experiences of many or most black people, at the time. Is it really surprising to you if, in the 50s, a black family’s interactions with white people are mostly negative, and often even very dangerous? It’s not too me. Maybe not every black family at the time had such experiences, but many almost certainly did.