My AP Government teacher taught us wrong material. When I corrected her, she called me a racist. Not to my face, but to students in other classes.

Eventually she complained to the principal, who had me sit in the office for the rest of the quarter instead of going to her class. At the end of the quarter she was fired and I was allowed back.

One thing I love about college is when you correct professors, they usually say "thank you" instead of calling you names.