I must take issue with the phrase, '...the proud racist defiance the GOP welcomed.'
You haven't backed that up.
Look, there are certainly some racists in the GOP. And it may be that some racists vote Republican out of a sense that Democrats represent black people over white (not my belief btw).
That doesn't support your claim of a flip.
Republicans didn't create and fight for civil rights because they liked black people. They did it because it was morally right.
Democrats who create and fight for set-asides and quotas likewise don't do it because they like black people. They do it for political expediency.
Removing barriers remains morally right. Awarding special privileges remains morally wrong.