It's kinda like laughing when you get tickled, it's purely physiological. You laugh even though you don't think anything is funny. You may even be mad as hell but you can't stop laughing. While there is certainly a psychological aspect to arousal, erections can occur in the absence of desire if the physical stimulation is present. Even if you don't want it, you may not be able to stop it. Add a restraint component and you have the recipe for rape.

We've all done gross stuff. Granted, maybe we didn't do it in class,but still...poor girl

Uncool to post that. Poor girl.