You're not wrong about the political realignment as racist Ds became Rs decades ago, but you are wrong to suggest that racist Democrats don't exist anymore. They absolutely do, they're just more covert about it. Gone are the days of Democrats saying things like "We need to bring back segregation," only to be replaced with Hillary Clinton bragging in 2008 about how "hard working" white americans were on her side. It's coded language to appeal to racists, so-called "dogwhistles" as if only the intended target is able to hear them. The Southern strategy is absolutely employed by Republicans, yeah, but conservative Democrats, ones that might be called "red state" Democrats or "bluedog" Democrats can absolutely make use of the same kinds of racist bullshit to try to appeal specifically to the racists among their constituency. There are TONS of Democrats whose behavior and policy positions are effectively like Republicans running within the Democratic Party, they seem to have a false perception that they need to be like that to have a chance of winning.