They are not really comparable terms of disparagement in any meaningful sense. They are different contextually and in how they are used situationally.
There is no gender connotation to bastard, the only reason it gets applied to men only is because when people want to insult women they rather use a sexist insult like bitch.
People use “bitch” to describe women who aren’t acting the way society dictates women should act, aka nice, polite, and submissive. That’s why it’s sexist. I didn’t know anyone used “bastard” anymore as an insult. Its kind of an odd insult because it’s insulting the person’s parents, isn’t it? Not the person.
I like “asshole” and “piece of shit” because they express exactly what one means.
I cut out the middleman and call them “son-of-a-bitch bastard.” 
so then what is a rat-bastard?
A untrustworthy or duplicitous bastard.
Windowlicker: pc or not?
That’s the point. It shouldn’t be an insult, yet it’s the worst word you can use. Why is referring to the female anatomy in a crude way so bad? That’s where the sexism comes in.
It’s like why calling something “gay” is considered homophobic. Why is being gay a bad thing?
Still, if you take this all the way, then you have to wonder why an asshole is a bad thing. Lots of people seem to love their assholes and those of their partner. Hasn’t stopped me from using the word, though.
I just avoid “cunt” because I know that people do take it to be sexist now, and I’m not intending to portray a sexist message. No point in getting banned in any places that have anti-sexist language rules, and no point in getting people to defend the shitty person I’m talking to because they care more about that word than whatever we were actually talking about. I just find crusades to try and preserve a particular word to be silly.
(I got banned on NotTheOnion–on Reddit–for mentioning [not using] the word. The later corrected the mistake, but the fact that “cunt” is on the list of autobanning words shows that it’s pretty mainstream on being considered sexist. When it’s a filter on Reddit that no one complains about, it’s pretty fucking bad.)
As for bitch–I still sorta use it, but much less than I used to. Very rarely is the gender of the asshole relevant. I mostly use it in verb form, since there’s really not a good swear word for the concept–though I do use “whining” a lot more often.
As for bastard–I see it like “lame” and “dumb”–no one uses it for its original meaning anymore. So I have problem using it. Still, it’s such a mild swear that I mostly use it facetiously.
In my lexicon, “bitch” would get used in exactly the same way as “bastard” both as a negative and a positive.
i.e. the same behaviours would get the relevant word according to gender. Same standard applies, different word used.
And they would get used towards male and females alike. Whereas “dick” or “knob” are pretty much exclusively male insults that are purely used for bad or substandard behaviour.
In the UK at least “bitch” is fairly mild. Indeed, just yesterday the office manager took a particularly strong verbal line with a contractor and was rewarded with an admiring “oooo! you bitch!” by the other female admin staff.
But that is the UK, YMMV of course.
You think you’ve got problems. I once (teasingly, losing in a card game) called my own son a “son of a bitch.” True story.
In the US, that is apparently the worst thing you can call a woman. According to friends of mine from Scotland, it’s a standard greeting for both formal and non-formal occasions.
Not quite. It was not that long ago that only sons could inherit wealth, so it was much worse for a man to be a bastard than a woman. The woman wasn’t going to get anything anyway, and had to be married off to someone to ensure her standard of living.
Did you not watch the first season of Downton Abbey? Poor Lady Mary… bypassed by some distant [male] cousin just because of her gender. 
Something that’s been alluded to but I don’t think stated explicitly in this thread is that “bitch” originated as an insult for promiscuous women, i.e. women who behaved like “a bitch in heat”. “Son of a bitch” thus presumably originated as an insult comparable to the archaic “whoreson” or the modern “your mother’s a whore”.
In modern usage I’d say that “bitch” is one of the few insulting terms for a woman that doesn’t necessarily suggest she’s promiscuous. That connotation hasn’t entirely faded, but today it more commonly means a woman who’s unpleasant or malicious. This is often used in a sexist but non-sexual manner to describe women who are assertive, aggressive, or outspoken in a way that might be acceptable for a man but is considered inappropriate for a woman. It’s also sometimes used in an admiring manner to describe a woman who’s assertive.
Interestingly, when used as an insult for a man then “bitch” still carries strong sexual connotations. A male “bitch” isn’t a man who has sex with a lot of women (such a man might be called a “dog”, though), but a man who is either willing to allow or unable to prevent other men from sexually penetrating him. This is actually pretty close to the older meaning of “bitch” in the sense that it refers to someone who engages in sexual activity with men that is seen as degrading. The term can also be used in a sexist but non-sexual way that is basically the opposite of what it means when used to describe a woman – it’s a man who’s not assertive enough but is weak/whiny like a (stereotypical) woman.
I agree with this ! Some men can’t strong women that stand up for their self !
My ex husband didn’t mind me sticking up for him but he didn’t like me sticking up for myself ! I showed him the door !
I don’t think either are sexist. It depends on context. As always and contrary to unsophisticated thought. Brief example.
“Bitch stole my fish!” Not sexist.
“Bitches can’t drive because they are bitches!” Pretty sexist.
“I’ve got 99 problems but a bitch ain’t one.” Could be true. Might be somewhat funny. Sounds sorta sexist.
It’s an insult directed at the man’s mother. Which is an insult to the man. Lots of cultures have insults that are directed at one’s ancestry. However, it seems like 'son of a bitch" doesn’t have the same interpretation it once did. But we live among those who commit many word crimes and are clueless about it. Like irregardless. Ugh.
Why is “stud” complimentary but “slut” derogatory?
Indoctrination by the patriarchy.
Then again, I see a lot of women who think that being an “effective manager” means acting like a bitch.
The patriarchy is full of idiots, shooting themselves in the foot for millennia. Look: All we men want to bonk as many ladies as possible, right? That’s what makes us studs. So wouldn’t the ideal strategy be to *encourage *promiscuity among the ladies, in order to maximize the number of willing partners around? But, nah, let’s do opposite.
Idiots.