The Democratic party of the South was White Conservative Christians. The nonsense, where people keep making it seem like the Democrats of today are somehow tied to supporting slavery, is just that - nonsense.
Yes, they definitely are tied to supporting slavery - it's their history, after all, they better know it, and learn the lessons this history teaches, anew with each generation that enters the world of politics.
Then, of course, we have the Party of Lincoln, devolving into the party of the Southern Strategy, and subservience to the plutocracy, a hollow, mean-spirited shell of its former self. It is by no means guaranteed that a formerly reached status can be preserved in the face of a morally and intellectually bankrupt party leadership - which should be another warning for Democrats.
Other than that, you are right, of course. And yet, the sad spectacle of a Republican party degenerating into something Lincoln would have beholden with utter disgust, isn't even half the story. At the very least, a proper diagnosis should include a media landscape and an outdated political system that render something as dysfunctional as the GOP viable, and also vast swathes of a near hopelessly brainwashed population that would even cheer on and support the moral demise of the G.O.P. to protect their unearned privileges.