The other day my sister and I were talking about a professor we both take music classes from. This certain professor is rather biased against violinists for some reason and my sister is a violinist. Anyway, I really like this professor because she's taught me a lot and is very encouraging toward me.

However, my sister recently informed me that this professor has been bullying her in her classes and most recently called her a b i t c h. I was a little shocked, but I trust my sister because she never lies about things like that.

Anyway, I can't even look at this professor now without feeling a tinge of hatred and I want to confront her about it, but I don't want to get on her "bad side" either. I am very protective of my sister because she's always been there for me and is in many ways my guardian angel. She even saved my life once when I was seriously contemplating taking it. It makes me furious to think of anyone hurting her like this professor did.

What do you think? Should I confront the professor or try to ignore it or what?