I had a very similar experience in my peds rotation. Our instructor was a woman who had no business being in a clinical setting, despite the fact that she had an MSN (she couldn't identify the ST segment on an EKG slide while trying to teach us rhythms in another class). She actually ended up getting fired after the semester of my peds rotation. She overtly showed in class whom she favored as well as the ones she did not like. Those that she didn't like happened to be most of the men in class. She would make snarky comments at our expense and come up with the most ridiculous things to say to us. Those of us she didn't like had never done anything to her or had any problem with her prior to peds. We'd really only had a couple of class days with her beforehand. But for some reason, she just did not like the guys in class.
I finally called her on it one day over a test question that came straight from our ATI book. She changed the answer to the question because she felt the ATI book was wrong. It was a question over a pain scale for peds. Several of us lined up outside her office to review the test. Well, one of her favorites came out before me and looked it over with me. We both recognized the question from the ATI book. We both put the same answer that was from the ATI book. I saw she had marked it wrong for her, but changed it. The favorite said she told the instructor she shouldn't change the answer from ATI and yada yada yada, the instructor gave her credit for the question. The instructor didn't know I knew this. So when I proposed I get credit for it and my rationale behind it, I was denied and told "I need to start using critical thinking skills" and how she didn't think I would pass this class.
So, I told her I knew she had given her favorite credit for the answer. And then when we went back to class and she asked how we all were after the test, I made some smartass comment, something along the lines of pulling answers out of her ass. And then I went to the dean.
And now she works in hospice. I feel awful for those poor people, having to exit the world with her at their bedside.