A certain percentage of the population suffers from antisocial personality disorder, and the internet offers them an outlet without physical consequences. This is both good and bad. It's good that they have an outlet to act out their natural aggressions & desire to violate other people's boundaries, but it's bad that others are on the receiving end. IMO sooner or later we'd all be required to use a citizen ID card to log onto the net, but that's for another discussion.
I've been around since the dial-up BBS and early usenet era, had plenty of encounters with people who enjoy hurting others and trolling discussion forums. Today you'd find them in MMO's and IRC channels, ganking newbies or pissing people off for the enjoyment of it. On the other end of the spectrum, you have a bunch of ultra-sensitive, self-centered beta-males who take offense at any general comment not directed at them.
One must understand that, in order for a troll to thrive, he must have a large pool of beta-male suckers with victimization mentality. If everyone was a self-confident alpha-male/female who doesn't need to get into an argument to justify their own positions, then the troll cannot thrive because there's nobody who cares to argue/debate with. Trolls feed on people's inner fears and insecurities.
-------------
As for the "chick" vs. <insert various degrading terms> argument, there's a time and place to use such words, such as "Serving Wench" at the Renaissance Faire. Walking into a corporate meeting room at work and commenting "hey that new chic in HR is hawt" in front of your coworkers probably falls under stupidity.