MLADEN ANTONOV / AFP / Getty Images A woman views the YouTube video of Amanda Todd in Washington, D.C., on Oct. 16, 2012

It was a bad week for Internet trolls.

News of the tragic suicide of 16-year-old Canadian Amanda Todd after an ugly incident of stalking, bullying and blackmail hit just as Reddit’s biggest troll, responsible for numerous highly offensive postings in sections with names like “rape bait,” was finally outed. Both stories involved nonconsensual distribution of sexualized images of young girls.

In Todd’s case, a pedophile who took a screenshot of her breasts when she was 12 stalked her online. She tried to escape by moving from school to school, but the perpetrator repeatedly posted and e-mailed the photos, making her a target for online and schoolhouse bullying. As word of Todd’s death spread, Reddit’s “Violentacrez” was revealed by gossip site Gawker to be Michael Brutsch, a 49-year-old Texas programmer.

So why do trolls do what they do? Clearly, we have an Internet culture that enables them, part of a broader society that piously decries the sexual exploitation of teenage girls, while simultaneously celebrating it in marketing and pop culture. The fact that Todd’s classmates could taunt a 12-year-old who had her topless photos distributed by a sick pedophile as a “porn star,” not a victim, speaks volumes.

The trolls themselves haven’t been studied extensively, but Brutsch seems to exemplify many of the traits that have been included in prior profiles. For one, trolls benefit from the lack of face-to-face interaction on the Web, which allows them to say outrageous things that would get them ostracized or even beaten if said in the real world. For people who are relatively isolated and feel powerless in their ordinary lives — as Brutsch appears to be — the Net provides a world where they can wield power and influence others.

Unlike most real-world bullies, trolls online can find a large ready-made audience that consistently encourages them, without any negative consequences. In fact, Reddit rewards users whose posts generate the most response by promoting them to the “front page.”

And public affirmation was certainly a driver for Brutsch. “I was playing to an audience of college kids,” he said in an interview with CNN’s Anderson Cooper last night. “[T]he audience was appreciative and supportive of the sort of gallows humor that I put out there.”

Reddit also offers real-world bonus items for its top participants, which egged Brutsch on. “Honestly, the biggest thrill I got was those meaningless Internet points,” he said, showing off trinkets he’d received from the company for winning those points, like a bobble-head doll in the shape of its alien logo.

Such “reward dependence” is a characteristic seen in many studies of antisocial behavior. And, indeed, trolling may unmask outright psychopathic traits like sadism that otherwise would often remain hidden. Oxford University’s Kevin Dutton, an expert on psychopaths, says, “People who have a nasty streak may have psychopathic traits like ruthlessness and lack of empathy.”

Both are clearly visible in Brutsch, who told CNN, “There are hot-button topics that you can make a comment about and just enrage people. Sadly for me, I enjoyed doing that. I liked going in and making people really mad over what amounted to meaningless things.”

One study of real-world bullies, which likely applies to trolls as well, found that the pleasure regions in their brains were activated when they saw other people being deliberately harmed — and the degree of activation was linked to their levels of sadism.

The anonymity of trolling for trouble on the Internet, however, may bring out a particular type of pathological behavior. In full-fledged psychopathy, there is a physical fearlessness that’s lacking in trolls. “They don’t act up in everyday life because they are frightened of sanctions,” says Dutton. “They’re nasty cowards, but when you get them on the Web, that fearlessness doesn’t matter anymore because there are no consequences. That’s the kind of person being unlocked here.”

Like other bullies, trolls also need to get a rise out of their victims if they are to enjoy the interaction. That’s why “don’t feed the trolls” is a constant admonition on many comment boards: their biggest fear is being disregarded and made irrelevant.

The best way to stop trolls, then, is to create an unfriendly environment. Reddit defends itself by citing everyone’s right to free speech, but just because something is legal doesn’t mean it’s ethical. The Net amplifies both the positive and the negative. That means that giving support to those who push content that sexually exploits teens — or any other type of objectionable material — only ends up making it more acceptable.

Brutsch and pedophiles like the still unprosecuted man who stalked Amanda Todd shouldn’t get social support on mainstream websites for fundamentally antisocial behavior. If removing this content from such sites only drives it underground, good: that’s where such trash belongs, making clear that it is not socially acceptable. If we want to prevent future tragedies, we need to be sure we stand with our daughters and our sons, not with those who would make them into involuntary “porn stars.”

MORE: The Tragic Case of Amanda Todd

Maia Szalavitz is a health writer at TIME.com. Find her on Twitter at @maiasz. You can also continue the discussion on TIME Healthland’s Facebook page and on Twitter at @TIMEHealthland.