Whack 'em. Giant rubber mallet. Works a treat.
Okay, seriously. Yes, there are jerks. They make playing games less fun, and can make it hard to get in the right frame of mind. Here's a few things to keep in mind when dealing with them.
Sometimes you can't just ignore them. I mean, there are coworkers, and sometimes they aren't awesome. If you have a job where you deal with customers, you will regularly encounter jerks who think that being mean to you gets them better results. But usually, you aren't allowed to just ignore them.
Mostly, the thing I do is start by considering how lonely they are. Think about it. If you're generally nice, you are constantly meeting interesting people that you like. They aren't. They're meeting what seems to them to be an endless series of fools, incompetents, and assholes. So they're pretty lonely. You might think they sure look like they're surrounded by people; they often are. You might think that it seems like people like them; that happens too. But if they don't really like the people around them, they're still not really getting that sense of connection that most people get from their social interactions.
Jerks tend to be lonely; this doesn't necessarily mean that lonely people tend to be jerks. In fact, there are lots of reasons for which people might have trouble getting the kind of social connections they want. My experience has been that people who are consciously aware that they're lonely are rarely jerks.
And that's where the skill of learning to hear what people mean, rather than the words they use, comes in. They aren't sincerely asserting a claim that you are less intelligent than they are; they haven't even thought of it. What they're really looking for is affirmation that they're smart, and important, and so on. Which is not usually a likely outcome of their behavior.
Me, I try to be nice to 'em. I don't go out of my way to bend rules for them, because why reward that kind of behavior? And I don't go around being all deferential to them. But I'm kind to them. And this does a thing, which is it offers them a choice between genuine kindness and their feeling of superiority, at a time when they are usually desperate for genuine kindness.