From an article published in the L.A. Times on internet trolls:
Trolls claim that they are motivated solely by "lulz," which is a corruption of "laugh out loud" — antagonistic laughter indicating the target has responded with strong negative emotion. Someone gets very angry, very sad, very scared — that's what trolls say they're after. The most problematic cases I describe, it's just about making somebody you don't know cry.
They're asserting power and privilege in an unmistakable pattern: They're policing against female-gendered behaviors — anything regarded by them as soft or emotional or sentimental. The idea of "raping with logic" comes up again and again. That's how they understand and celebrate their behavior.
A good article on trolls on the internet. It's based on research by Whitney Phillips for her book This Is Why We Can't Have Nice Things (which will end up on my to read shelf soon).