The switch in black voting patterns wasn't due to a change in black attitudes, but because of a near-reversal in political parties. The Democratic party was once the party of the Confederacy and States' rights, while the Republicans opposed it. By the 1960's, this was reversed.
The Democrats and Republicans changed, not the black voters. Similarly, as Republicans become more liberal (which is happening as we speak), I have no doubt that more ethnic and racial minorities will start to vote Republican. The point is, it's not the party label that matters, but what (if anything) that party label stands for.
That is a myth the left created, the actual reversal took place in 1936.
See post 51.