The rapist is the only one causing the rape. Not both perp and victim.
I just don't think it's as black and white as that in many cases. The girl who goes out to a party where many people are hooking up, gets stinking drunk, too stupified to say no, and hooks up with a guy who's also drunk is vastly different from the evil predator who preys on women. I saw situations like this happen between friends of mine - I can remember one particular case where a girl was coming off a breakup and got near blackout drunk, then was basically dragged to bed by a friend of hers and she was pretty pissed afterwards. He clearly had feelings for her, went into the night trying to make his move now that she was single, they both got really drunk, and it ended unfortunately, but that's a volatile mix of circumstances where many people aren't at their best (particularly at age 20). Was that sexual assault/rape? By the letter of the law, probably - she was too drunk to consent. Did he deserve to spend the next 10 years or whatever in jail? Hell no. End of the day it was an asshole thing to do, but they both moved on from it and recognized it for the non-world-ending offense that it was.
The number of people who try to romanticize rape out of what it usually is is disturbing.
So do you think my friend should have gone to jail for a few years? I don't think "romanticize" is the right word here either... I don't see anything romantic about what happened there, it was messy and unfortunate and disappointing, left both sides feeling bad.
And just to be clear, my personal view on rape and enforcement is that it's basically impossible to get the laws right. Life isn't always black and white. The example I provided above illustrates a case where I believe the current standards wouldn't work well.