"Jock idiot" sounds like a stereotype primarily aimed at males, while "cunt" is a vulgar term for the female anatomy. Can you explain why "cunt" is the appropriate pejorative, here? Does your view of the definition of "cunt" differ from its colloquial meaning, which I've always interpreted to be, "Someone who is the very worst possible sort of woman?"
In the UK 'cunt' is used against men more frequently than against women. Calling a woman a cunt is somehow more rude, but it is a general word for a terrible person. There is no gender barrier for its usage. Furthermore, 'cunt' is often used in a friendly manner here. I call my male friends 'cunt' all the time.
Well, you see, this is the thing about words. The 'definition' of cunt is that it is a vulgar term for the female anatomy, but definitions are static and really don't tell us an awful lot about actual use of words. When I call someone a "cunt", I basically mean that they are a bad person. And even if the word has sexist connotations, I am only saying that they are a bad person, not "they are a bad person, and I use the female genitalia as an analogy for their badness."
I think my opinion of cunt changed a lot when I lived in Australia. Rather than being a derogatory hate word for women, it is used more often between friends, especially in a pub environment. As of late, my brother has been making some immature, ignorant comments about general life circumstances and I suppose my use of the word cunt is a comeback of sorts to those comments that are, at times, so ridiculous that they don't merit argument. I suppose it is a way to try to get him to realize that he is saying stupid things without putting too much effort in.