I think it's old hard-wiring, left over in the brain from the Cro-mag years or something. Pack mentality. The beast is bleeding, quick everybody get em! We all fall into it now and again, nearly all of us anyway. It can be hard to resist in a moment when you "feel so right" about something, or maybe just pissed off about some stupid unrelated thing and end up taking it out on some dude who just doesn't happen to like a purple sparkle tort guard on his made in China Ric copy.
I always feel like a total jerk afterwards regardless of the actual right of the matter, and it happens less and less because of the self inflicted shaming I undergo. I'm trying to be good TB, I swear. But I'm only human, and weak.