of bitches and other linguistic conundrums

so i was thinking last night about the word "bitch". we all know that a bitch is a female dog (and possibly other animal varitites?), but we also know how it is used. so here is my question:

female dogs are submissive to males. when a bigger or stronger or more alpha dog comes along, the female will flop onto her back and expose her belly for petting or ripping apart. when they mate, the female is practically getting raped, and she just kind of stands there and takes it while the boy dog (with no nasty nickname) runs his agenda on her. a mother dog will nurse her puppies and try to protect them, but if someone higher on the totem pole walks over, she will even let them take away her babies.

so why is a powerful or assertive or aggressive or pushy or strong woman a bitch? why is a woman who walks into a boardroom and commands respect a bitch? why is that bad driver a bitch? why is someone who screws people over a bitch? i'm not commenting on whether or not these people deserve our scorn or deserve to be cursed out, i am just wondering why they are labeled as something that is almost the complete opposite of their behaviour.

it's not like it's said in sarcasm, the way you tell an idiot that he is sooooooooo smart. it's not said condescendingly, like you are taking them down a notch by slyly calling them weak and ineffective. no- the word "bitch" is used as the ultimate condemnation of all things ugly. and it's not even accurate.

so what's up with that? other swear words pretty much fit. i'm not gonna go through a list, but they usuallly prettty accurately describe the situation. bitch just doesn't seem to fit.

any insights into this bastardization of language, or am i just being a bitch?