The argument that Democrats are the real racists stems from racial policy generally coming from their side, like affirmative action, as well as the progressives, who've been dominating the
vocal demographics, being largely racially motivated. Also, the Dixiecrats in Congress never left, they just stopped talking about Jim Crow. You've also got
Verified Hate, which is a hashtag, and an obsessive Trump supporter (the latter of which is what I linked, because that particular Gab account is pretty much solely the relevant content), that cover verified Twitter users spewing racist horseshit.