Stephan is a nice guy. Girls like him. He votes Green. Adores and respects women. Went to the Women's March.

But when it's fapping time, he clicks on something very un-feminist: girl fights. Real girls with real anger in parking lots and on beaches roiling. And when girls slam girls pavement-ward and wail away, all of his "This-Is-What-A-Feminist-Looks-Like" sympathies vaporize and his dick stiffens like Quikrete.

Stephan told me about this only with the understanding that I would not use his real name. "People find out I get hard when chicks go hard, you might not get invited to parties," he says.

In a way, his fetish scares him. His brain lives in 2017's sophisticated politically correct feminist urban America, but his dick lives in a cave in the Stone Age. "It makes me wonder what other ugly stuff is down deep in my psyche," Stephan says.

Stephen is an agonophile, or someone who gets sexual arousal from fighting. He is not, however, the only filthy animal.

These girl fight videos have hundreds of thousands or even millions of views. WorldstarHipHop thrives on it. There are YouTube playlists of nothing but girl fights. Girls fighting at house parties. In kitchens. On beaches. As proof that it isn't a sideshow but an aphrodisiac, these videos are increasingly featured not just on YouTube, but on porn sites like TubeGalore and YouPorn. even has an entire subsite called Ultimate Surrender, where helmet-clad women engage in what they call “hardcore naked female wrestling porn.”

Seinfeld even devoted a big chunk of an episode to it, and Jerry said men like it "because men think that if women are grabbing and clawing at each other there's a chance they might somehow kiss."

It's not a new thing, that people like to watch this stuff. Porn pioneer Irvin Klaw made staged tame girl fight videos in the 1950s, using actresses, including Bettie Page. Girl fight vids grew in popularity through the 1960s and 1970s, in movies about women's prison and roller derby. In the 1990s, girl fights fueled the popularity of The Jerry Springer Show. This century, it's the Real Housewives and Jersey Shore tearing hair.

What's new, then? Cellphones. The camera in your pocket is able to record real street fights. In many of these videos, you'll see a handful of people with their phones out. These brawls are more barbaric than the staged fights, and therefore so much more gripping. So, they've lead to an explosion in the number of girl fights on the Internet. Here's a classic: 

Let's put on our psychologist glasses for a sec and ask: What's behind men taking sexual pleasure in something so brutal?

Here are six theories.

One: Evolution made dudes dig violent chicks. Men want to mount powerful women so they'll sire warrior children. The Vikings armed their women; the powerful ones lived and mated; Scandinavians are huge today. Even on Tinder, fierce females with knives and scowls gets more right swipes than hippie chicks.

Two: We're fantasizing that they're fighting over us.

Three: In our brains, sex and violence aren't opposites, they're neighbors. Researchers found that the neurons in mice brains that fire when they brawl other mice are "intermingled" with the neurons that fire when mice fuck. Sex and fighting are both associated with adrenaline.

Four: Our dicks and minds are confused about what's amping us up, and we're misinterpreting the adrenaline we're feeling watching fighting as sexual arousal. This is the thrust of a psychological concept called "misattribution of arousal." People in intense situations — war, the first day of college, being kidnapped — feel the fluttering heart, the racing thoughts of fear, and think it's lust. This is why people fall in love with their kidnappers.

Five: It's about the girl being devalued and degraded. It's the same thing that makes piss vids hot. 

Six: It's a borderline snuff film. These men might be "closeted misogynists who (perhaps unknowingly) long to kill actual women," writes Chuck Klosterman in Esquire, and so when they watch girl fights, they're "unconsciously hoping to see footage of a woman being murdered."

That's a pretty intense explanation, though. And it's nullified in part by the fact that women say they're into seeing women fight, too. It flips the script. Women want to be aggressive and ferocious, but they're not socially "allowed" to, so they imagine they’re one of the girls fighting. Catfighting "goes against most ways our culture imagines women to be, and thus creates a lot of curious interest,” psychologist Will Meek told NBCNews. Women, too, get off on violence — as many as two-thirds have rape fantasies, enough for a brand new movie on that sort of dark fetish to get rave reviews.

As a woman named Koko colorfully explained on a forum thread called "Female Single Combat Club," "I saw a really good long drawn out fight at school last week and the effect on me was sensational. My breath came in short pants, my heart was beating so loudly I thought it was going to jump out my body. I felt such a thrill I thought I would pass out with delight. More than that, my pussy was delightfully moist. After the delicious fight I went to the girls' toilet and frigged my self, remembering with delight the thud of the punches and the smeared blood over the fighters. The thought made me cum three times in a row. There is talk of a rematch, so time to wear my skirt short and show some cleavage. If the rematch takes place-and there will be plenty of us girls there to watch it because we love the first fight sooo much. I can’t wait."

Is there a lesson here? Some point or takeaway? Maybe it's more evidence that the range of sexual fetishes knows no bounds. Maybe it's that there's a darkness down deep in all our souls and dicks. Maybe it's that we're all more animal than we think. Whatever the motivaion, whether healthy fantasy or sick twisted sadism, guys — and some women, it seems — it's basically becoming its own genre of entertainment. "Bad Girls Club," anyone?