Let's say there's a girl (G) who has a boyfriend (B).  And it is the belief of B's friends that certain intimate things go on between G and B.  And it's all kinds of shocking or hilarious or whatever because B has always been shy with girls and the last person anyone would have expected to be getting any of anything.  So then B breaks up with G and she is totally devastated.

What exactly would make B's friends decide that one of their new pastimes will be sexually harassing this girl?  To come up behind her while she's at her locker and dance-hump her (term courtesy of J.R. Angelella) and make sexual tongue motions in her direction when she might or might not be looking and laugh about it during and after?

Are they letting the world know that they think: "This girl is such a whore that this is all she exists for"?

Are they saying, "She is so ugly/crazy/otherwise unappealing that I would never want to tap that, so hey, aren't I being funny and ironic by doing this"?

Are they like, "I am so into her.  I hope she wants to give it up to me now that she's single.  This should be a really great way to get her attention"?

I'm asking these questions because, yes, something like this happened to me in high school.  But also -- mainly -- because something like this happened to my main character my current project.  To get these scenes right, I really NEED to understand the antagonists in these scenes, but I don't.  I never have.  And obviously, I'm a little too close to the subject matter to be objective.  (For the record, I always assumed their thought process was one of the first two options, but someone else suggested to me yesterday that it might be the third.  Which I find ludicrous, but what do I know?)

I actually considered writing to those real-life antagonists via FaceBook to see if I can get a response out of them.  Alas!  They don't have FB pages.  (Also, it's possible that I would have been too chicken to go through with it even if they had.)

Can anyone else shed some light for me?