I understand my response would appear rash in context. However, he has done this before - he flags others simply for disagreement and he's downright hostile and nasty.

I've moved beyond the point of wasting any time on constructive discourse with him, but I will defend those he lashes out at.

Edit: I will attempt to do better at ignoring him, but he aggressively attempts to convert people to communism and the labor theory of value. He cites to Stalinist webpages. Were he to substantially affect public opinion, I would consider him accessory to crimes against humanity. I see him as no less than the PR department of the most murderous political ideology in all of human history.