It pains me that I have to say this. That it's not so obvious it can remain unspoken.

By now, a lot had been written about the gang rape of of a 15 year-old girl outside a high school dance in California. And a lot of people seem to want to write off the fact that as many as 20 people watched or participated in the brutal, 2-hour assault as just the latest example of the bystander effect.

Now, the bystander effect is real. What it means is that the more people are witness to a crime, the less likely anyone is to do anything about it, because everyone thinks someone else will do something. (BTW, if you ever witness a crime as part of a group - please don't make this same assumption. Do something!)

But the bystander effect wasn't the primary force at play here. How do I know? Because people weren't just standing by, horrified. They came to the scene when they found out what was going on, called there by texts and emails. They came because they wanted to watch or participate. They weren't passively paralyzed. They were actively involved.

It's also been said that "street culture" is to blame. That local gang violence had inured these kids against the horror of what they were doing/watching. And it's true that when an entire community is poor, violence increases. When kids don't think they have any better options, gangs are more likely to seem appealing.

But let's dismount our class-privilege high-horse for a minute and consider: what if this had happened at a frat house at an elite university? It's pretty easy to imagine, because rape isn't an act that's linked to poverty. And if this hideous assault had happened in that elite setting, we'd all be saying it was allowed to happen because these are the children of the wealthy and they believe they can get away with anything.

It's understandable to want to find meaning behind such an unthinkable act. It's human to want to figure out why it happened, so that maybe we can prevent it the next time. And the sad truth is, the answer's just not that complicated.

It happened because, in the absence of comprehensive, pleasure-based sex ed from an early age, kids are learning about sex by watching gonzo porn that fetishizes violence against women.

It happened because rape is literally treated as a game by the powerful video game industry.

It happened because Whoopi Goldberg and scores of other Hollywood heavyweights made it perfectly clear that if you're talented and powerful, it's no big deal if you drug and rape a 13 year-old girl. And who doesn't want to think of themselves as talented and powerful?

It happened because when women accuse men of rape, we automatically question her motives, which leaves rapists free to rape again and again.

It happens because movies treat rape like a punchline, and pop music treats women's bodies like trophies or dolls.

It happened because we live in a rape culture. And if you're not actively working to undo that, you're supporting it. And we're all reaping what you sow. Including that 15 year-old girl who's going to have to live with this unspeakably brutal violation for the rest of her life.