Actually, there's a maximum number of times you can downvote someone, presumably so people can't vendetta against someone if they get their feelings hurt. So, maybe they can't do it.

Sidenote: I think Steve Pavlina created a joke word for people who are totally normal and in control, and then flip out randomly over nothing online in a comment thread - "Kittywompus." I'm not sure where the word came from (maybe he had a cat that was relaxed most of the time but then flipped out occasionally?), but it's definitely a real phenomenon.

I still don't understand the roots of it myself, on the rare occasions I get upset online I close my laptop up and go out for a walk... it's like a circuit breaker, "oh shit, I'm losing the ability to think clearly, I better get out of the environment" - I think most people have something like this, but maybe a few lack this circuit breaker?