Whether or not it's active racism, or subconscious racism, or "white guilt" (sometimes aka "well-intentioned racism), the left is actually /hyper-focused/ on race, "people of color this", "people of color that", "reparations", "affirmative action", etc. etc.
And if you don't believe there's any subconscious racism, check out this video; "Ami Horowitz: How white liberals really view black voters":
https://www.youtube.com/watch?v=3JGmKHrWKMQ
Yeah, there are some real alt-right trash trolls on the site, but no, I don't really know who they are. I see people keep mentioning "purgey", but I never saw his name, and don't know his alts. I barely pay attention to names in any case, and if I see a bad enough meme from either side, I downvote, flag and forget.
Gotta remember that racists, like trolls, thrive on attention. If you let them know that what they say bothers you, that gives their words power and they'll keep doing it. If they can't get a reaction, eventually they'll go away and try it somewhere else.
Thus the phrase "Offense can only be taken, not given".
(Though I'll grant it might take a little longer for them to go away from a site that makes it so convenient to make memes to post somewhere else.)