I actually almost walked out of a class in college due to a professor not believing my answer (in fact when I tried to give it as an answer in class he kept telling me "no no no no" and wouldn't even let me speak!! In the end my answer was correct but according to him I used something that was too advanced and he didn't want the class to hear it yet because it would confuse them.
(I honestly think it was just an excuse for his silly behavior before).
I also had problem in my HS government class because I grew up in a part of the country that was very extremely on one end of the political spectrum and I was only one of two students in that class of 30 who were on the other end (the teacher actually tested us at the beginning to see "where we stood"). So yeah, I tended to get some pretty poor grades on essays during that class...
