I don’t think he was saying black family’s were better off “because of” Jim Crow, but that in those days most families were intact, kids had two parents, they had traditional values, day care was not a major expense, and the schools were good.
It’s not what he said or meant - it’s how it was taken; and he should have perceived that. It’s a basic political sense to watch one’s words with an eye toward how they’ll be twisted. It’s more so now than ever in our political history.