I pretty much use geek and nerd interchangeably and no matter how you look at it there's a lot of crossover.
I don't know if you'd consider me a nerd or a geek. I'm basically an expert on Star Trek. Passable on Star Wars. Familiar with some basic comic book lore but don't actually like comics. I play Magic the Gathering. I collect, assemble and paint sci-fi miniatures. I play tabletop war games. I obsess over franchises like Terminator, Predator and Aliens. I read the Song of Ice and Fire novels before anybody at HBO had ever uttered the words Game of Thrones. I could go on and on. My housemate is exactly the same. We've just spent the last 12 hours or so playing Magic the Gathering together. That was our entire Saturday. Nerds, geeks, whatever...we're certainly something. And we both love Big Bang.
I don't expect mainstream comedy to be particularly realistic. That's why I tend to stick to things like Party Down. Or, better yet, high-end drama with good comedic elements. The Big Bang gang are not all that believable as serious scientists, but then again, maybe my idea of what a real scientist is is outdated and not so applicable to my own generation.
Barney may not technically be a rapist, but it's pretty damn close when you ply a woman with alcohol and then lie about every detail of your life in order to make her have sex. I seem to remember one where he convinces a woman he's from the future and she must have sex with him to save all of mankind or something. You know what, fuck it, I think this should constitute some kind of rape. Statutory rape is a thing. This should be a thing. Maybe. But whatever, it's despicable and it's in the same ballpark and I have seen many episodes where his friends encourage his behaviour, even assist in it. It adds to rape culture. Even if he grows as a character, you don't get that when you just watch an occasional episode. And you don't get that if you're an idiotic and impressionable young male.