I feel that often times people believe that they're at the forefront of intelligence, and take offense if someone is more knowledgeable about a subject in a significant way.Everyone corrects people on everything they can when they're not deliberately trying to impress whoever they are talking to. But there is a line at which people take offense, and start classifying the person as "that guy" who "knows everything best", even though the intention in his behaviour is the exact same as everyone else.
If someone tells you that you're wrong, and then promptly explains why, then he's not being a dick. He's doing the exact same as everyone else, but he happens to receive more chances to do so, which everyone takes 100% advantage of, given the chance.
When I see people with this mentality, I find it to be very hypocritical, because everyone wants to be judged by their intentions rather than their actions, but then go on to deliberately go and do this just because they're clearly insecure. This is the same as when someone insults someone who is in excellent shape by calling him stuff like "health nut", and propagating the myth that elite athletes are destroying their bodies etc.