I hardly mind to be called a bitch, more so: I enjoy it because it means I was succesful in a particular situation wherin I attempted to be a bitch. So I smirk and blow a kiss or make a jack-off gesture - depends on the person I succesfully irritated.
Though, there's also a bit of a language thing to this. 'bitch' is actually used commonly in my language (with a heavy 'jest' weight), the Dutch equivelant (as a swearword) not so much anymore... 'whore' particulary (and variants), and 'slut' (and variants) are more popular, especially when combined with diseases.
Hmz, though I'd probably still smile if an English native-speaker called me a bitch...