I know it's popular in conservative lore to preach that it was Goldwater's drubbing that gave us Ronald Reagan. I think, to your point, it was Goldwater's drubbing that gave us a permanent disadvantage in the black community. And, it also gave us Johnson's "end poverty" initiatives, many of which are still with us.
Goldwater's loss wasn't a turning point for conservatives. But, it may have been the stake through the heart - a very slow moving stake through the heart. Sure, we had Reagan in the interim, but Reagan's tax cuts are long gone and Johnson social programs are still here and are about to get a whole lot bigger.