I'm fairly certain it doesn't happen only in classes that have a focus on the arts, but as my studies were inclined towards a degree in creative writing, I can say that I did see a lot of the pretentiousness you both describe in Literature-based classes. Probably the most annoying example of it was this guy in my Film Appreciation class who would hijack class discussions for 10 - 15 minutes while bloviating about what he thought was REALLY going on with the movies we watched. I don't really remember anything of substance he actually said, but his favorite phrase - I heard it thousands of times - was, "In a sense..." My fingers developed this tic that caused them to twitch whenever he said this phrase... it's entirely possible they were aching to kill him.
Brian brings up a series of fair points. It makes complete sense to me that professors would be taught to adopt the superior air, if only to shoot down the idiots who want to mess with their heads and turn the class into a waste of time. Teachers can't afford to get their cages rattled, especially early on. It's only further into the year, when there's a rhythm established, that an educator is going to feel comfortable releasing a little bit of control to the students who actually WANT an education, versus the morons who're just there because their moms and dads are making them.
But while this all describes what happens within the halls of education, it's a sad thing to remark that one can find equal pretention in fields of other employment. Even in something as mundane as carpet cleaning, which is what my career currently entails, one can find a lot of pretention and a LOT of idiots. It's not just the customers I describe in this case, although we have plenty of morons who seem to think we can't tell when they're lying about particular spots or stains... it's the employers, too. I can't tell you how many times I've been condescended to because somehow I've failed their expectations with regards to adding on high-dollar unscheduled services. The region I live in is very conservative and it's a very difficult thing to get customers to let go of their money, and I make an honest effort every day toward that end... but honesty is also IN the effort I make, and that means not shystering the people who pay me into purchasing something they really don't need. I'm a salesman, but I'm not underhanded. My bosses seem to fail to understand any of this - they live in a much more urban area and are accustomed to easier customers than these, and to my knowledge they have never once tried to operate the kinds of routes they send me and my co-workers on. Until they do, they will never understand the difficulty we face here... even though the employees from that urban area who've visited our territory have consistently confirmed our protestations as to the difficulty. The bosses don't want to hear that. They just want their money.
It frightens me, actually. If that's going to be how it is in a simple carpet cleaning business, how is it in other venues of employment?