I figure they both are telling the truth. Hey I know liberal professors screwed me in college just because they didn’t like me even reviewing a book that didn’t agree with their revisionist version of history. I mean a low grade because I dared review a book that said reconstruction of the South after the Civil War was a mistake.
So it does happen. But I didn’t sue them. My recollection is a lot of professors and a lot of students are jerks.
In my first year of college I had a prof who had a reputation as a liberal if not socialist/communist. The coarse was something on modern writings and world affairs, Lippmann, Marx, Hitler etc. In the final exam there was a grade important question about what was propaganda. My written answer was that most of the assignments we were given were propaganda. I was given an ‘A’ for the course and to this day remember the prof as a very fair person.
Maybe you received a low grade, not because of the subject matter of your review (which I fail to see as being conservative or liberal), but because the review was poorly written.