Yeah the racism thing was long enough ago that most people today don't remember it. It was pervasive though, at least as pervasive as homophobia in the church today.

The idea that God had created the races to be separate was so baked into Evangelical Christianity that it was inseparable from Evangelical Christianity.

By the early 1970s, cracks started to widen pretty dramatically as Evangelical Christians like Jerry Falwell and Bob Jones feuded with one another over racism. Bob Jones insisted that separation of the races must remain a core principle, while younger leaders like Jerry Falwell (the father of the current one) struck out in new directions.

Ironically, soon after he stopped preaching racism, Falwell went on an anti-LGBTQ rampage, apparently either consciously or unconsciously aware that he needed an enemy to rally his followers against.

Jones fought on hard, rallying his followers around the separation of the races. But as the American people grew more and more wary of overt racism, his stand became less and less popular.

Then the IRS revoked Bob Jones University's tax exempt status, and the Supreme Court upheld the revocation. After that, Christian organizations were pretty much on notice. Drop your racist practices, or face an existential crisis that you will lose.

And that pretty much spelled the end of official racism in American christianity, although traces of it linger like with your uncle.