To be honest, I used it because Rivier originally did (yeah, I'm totally going to blame her :p) and frankly, I don't really have a word in my vocabulary that quite carries the same connotation as "acting like a cunt", in which, for me, "cunt" stands for "wilful, persistent, deliberate asshole" It conveys a certain belligerence and self-awareness that I don't really have another word for. You can accidentally act like a dickhead, but you can't really accidentally act like a cunt. Maybe the more American "douche"? But that's also vaginal in nature, so I can't see how it's much better.

I personally use a lot of genital insults, I don't really know why, and for me they really don't have any sexist connotations, though I can see how they would for other people. I'll try and think of a better word. Damn.