> But all educated Americans know that the parties flipped their positions in the 1960s when Dems under LBJ courageously pushed out the racists to pass the Civil Rights Act and the racists moved to the Republicans.
That is an oversimplification.
What happened is that overtly racist policies fell out of favor. People talk about structural racism today, but nobody can say with a straight face that it's the same now as it was in the days of Jim Crow laws.
By the 1960s the Democrats saw the writing on the wall. The political winds were changing and they adjusted their sail. But supporting Jim Crow had been how Democrats got elected in the south. By voting with the Republicans to pass the Civil Rights Act, they alienated all the old racists who voted for them specifically to prevent that from happening.
The south was ready to skin them and eat them at that point. The Republicans weren't too stupid to realize that. All they had to do to take the south was to show up and be Not The Democrats.
Some racists (e.g. Strom Thurmond) switched parties, but in general the Republicans were never as racist as the Democrats historically were. They didn't have to be. Popular support for racism has been on the decline for more than a hundred years, and the remaining racists no longer trusted the Dems so the Republicans never had to give them anything or even really promise to give them anything to get their votes.
It's not so much that the Republicans flipped as that the racists lost and that redrew the electoral map.