I'm pretty hard on teachers, sometimes.
My reasoning goes: I'm about as smart as anyone else taking this class, and I'm working pretty hard. If I don't understand what you're talking about, then you aren't communicating clearly. Try again.
Depending on the day, I may be more or less sure of this statement, though. For one thing, it's pretty arrogant. You'll notice that I chide myself for arrogance pretty often, but I never stop doing it.
It's arrogant, because there are people who are actually less smart than me, but they work much harder, and they get it. Or people who are as smart or smarter than me, who have no problem. Also because I usually get the concept once I stop complaining about it and try reading a bit.
Then again, I think it's fair to hold teachers to a high standard as well. I had an exceptional teacher last semester - Patricia Wrean. Good math teachers, I believe, should be given knighthoods and and millions of dollars, but instead all they get is the same salary as every other teacher. Logically, then, we should hold every teacher to the high standards of exceptionally good teachers.
Now, it's true that the teacher in question is a genuine rocket scientist, but that's not what makes her good. The difference was that she analyzed the performance of past students (using advanced statistical models - she is a math teacher), sought feedback constantly (do you like the colour of the pen I'm using? Is the text big enough? Do you get this concept or should we do another example?) and overhauled her curriculum every year.
Every teacher should do this. Not all of them are smart enough. Not all know how. Not all are willing to make the effort. And I'm pretty sure none of them get paid enough.
Anyway, if I'm hard on teachers, I'm just as hard on myself. They seem to enjoy me, too.