Well traditionally insults to women are either related to animalistic characteristics (bitch, dog etc) or sexual availability (whore, slag etc)
where as men are insulted as sexual organs (e.g. c**t, dick, twat etc)
Gays seem to swing between both styles, with effiminacy oftem matching to more womanly insults.
These rules do seem to be breaking down.
For example Not a Dr Jillian McKeith, is clearly a c**t, a twat and a suppurating syphilitic penis.
She is not a slag or slut. That would imply wanting to have sex with her, which is just nightmarish.
You couldn't call her a bitch or cow, as the RSPCA would be onto you for defmaing animals.