Look up the SF X Tekken Cross Assault debacle and how the internet reacted to it. It's not advocated at all, but people will generally use the anonymity of the internet as a means of being an ass. Case in point, this website.
Wait are we talking about being a troll or being evil? I thought being a troll meant being annoying but without any realistic, harmful intent. You guys are wandering into "actual misogyny" territory.
What I originally came in here to say was, I troll girls because I spend a lot of time around them and I know how to push their buttons. I was questing with this player and she said... I don't even remember, something like her breasts were bothering her. So I said "Well then take them off for now." Naturally she was a little jarred. She tried to explain anatomy, and I kept asserting something I knew to be false. "Um, they don't come off." "Have you tried pushing them back in then?" "It doesn't work that way!" "Would you at least try it before being so negative?" "Woooow... have you ever even seen a girl without clothes?" "Yes, and those Barbie dolls are much less condescending."
People usually feed me a decent serving of Nooby Snacks before brushing me off, and then we move on. Guys don't react the same way. It's just not possible to troll both genders the exact same way. I wouldn't say I advocate trolling in general, but to answer the titular question: games are an environment where I don't have to be my serious self, so I choose to entertain people.
You opened a debate, and I'll be damned if you're not going to finish it. ~smashbrother3