You really want to be on the side of good but you are not. You, personally, are probably a really good person but, if you are a registered Democrat, the party you are in is not. It does not have a good history. And yes, it was the leftists, the Progressives who were the racist ones.
But here is the thing. Liberal or conservative, Democrat or Republican, once you go back into history, before the Progressive era, you will find that what we consider racist today applied to everyone back then. Some were worse than others. There were many great people on the right and the left prior to the Progressive era, who did amazing things for this country, but were flat out racists.
However, everything that was done that benefited whites is fully applicable to all races. Democrats didn't make that happen. Democrats weren't even pushing the issue until LBJ was president.
There was no political shift in the 50's and 60's, there was just a tactic shift on the part of the Democrats. Where the political shift happened was more about labels than anything else. That happened in the Progressive era when the Progressives wanted to be called the more favorable term, liberal. They wanted everyone to think that their oppressive Marxism was being done in the name of liberty. And the succeeded in hijacking that name and called us, the true classical liberals, conservatives. Now you guys are doing everything you can to convince yourselves that we are Nazis and fascists. We never were. That was always you guys. That is who the early 20th century Progressives were and they did not hide that fact until the 30's.