There was plenty of evidence of MLKJr being Commie-influenced going back to the 50s but I’ve never seen anything that had him as a card-carrying CPUSA member.
Look I’m not overly enamoured, or at all, of MLK but the simple facts are the democrats would have done anything to hurt him because he was telling Blacks that skin color wasn’t important. And that directly conflicted with the democrats work to divide the nation by race, a game plan they still embrace.