You're very much mistaken. I don't know why Republicans think that pointing out something that is no longer true -- that the Democratic Party of the 19th Century was the party of southern racists and slaveholders and that it defended Jim Crow and discrimination until the mid-20th Century, when the party drove out the racists -- can somehow have any bit of relevance to the plain historical fact that the driven-out southern racists found their new home in the Republican Party. This simply can't be denied. It's nowhere close to saying *all* Republicans are racists, just that most racists vote Republican. 

Pointing to old history that's no longer the case cannot absolve today's sins of the GOP. Democrats repented and changed. GOP still needs to face it.