First off, if you're talking about outright racism, trying to block black access to voting (and women voting), and funding groups that were literally meant to exterminate the population of color, I'm sorry but you're talking about the 1920s and even later, not the 1800s. Second, this completely misses the point. Democrats say they absolutely cannot be racist essentially because they just call all conservatives racists, but they have very racist ideas themselves. For example, requiring voter ID is racist because black people won't be able to register. Registering isn't hard, and to suggest the black majority is too dumb for it is extremely racist (but you never hear this perspective). Now, I think this is really just a cop out so they can continue cheating, but still. And defunding police in black neighborhoods just exposes them to more crime, which will lead to an upward spike in black deaths. And there's many more examples of modern racism in the Democrat party. So when people say "Democrats have always been the party of racism" they mean that they've never really changed. They've flipped their appeal to get votes and gotten the people to think they're supporting the right thing (which, fighting against racism is the right thing to do), but the politicians never really changed. They mask racism but it still eeks out every once in a while.
Whereas comparing whites now to the 1800s is not even close to accurate. Very few people are trying to enslave blacks still, very few are looking to hurt blacks at any chance they get, and very few are against black rights to vote or be human. Most white ppl Ik don't even think about blacks anything like blacks think about whites. Black ppl are always talking about white ppl but you never hear this kind of attitude from whites. And you could argue for or against black ppl are justified in doing this (that's a whole nother argument I'm not getting into here), but the point is, 1800s whites and even 1900s whites are nothing like they are now. And young white ppl on social media these days just seem really stupid with all this virtue signaling and trying to educate people on history they know nothing about. But that's also because of the Democrat situation.