This is one of those posts that wouldn't exist if I weren't semi-anonymous.
There is a certain very senior colleague of mine who is in a closely related field and who has zero research activity and zero visibility in our field and zero graduate students. He is, however, very aggressively patronizing toward me, routinely saying directly and indirectly that my research and teaching are flawed, misdirected, boring, and not rigorous. His refusal to consider retiring is very annoying, but his continued professorial existence is not entirely a negative. Other colleagues and I get a laugh out of the amazingly rude and obnoxious things he says, and the graduate students do a hilarious impression of him.
One of the courses for majors that I am teaching this semester has many of the same students as a course that he is teaching this semester. His class is just before mine and in the same classroom. Yesterday, he asked me what I thought of the students' collective mood at the end of his class and the beginning of my class. I said that their mood was generally positive. He then asked "And why do you think that is?". I thought of several possible responses, all of them rude, but then settled on what I believed to be true: "It's a really nice group of students who seem very engaged in their major classes." He said "I can think of another explanation." I didn't even ask what this was, knowing the explanation was inevitably coming anyway, but another professor listening to our conversation naively asked him to explain. The answer? Because they know the rigorous class has finished and they don't have to think much during yours. Maybe he's in a secret faculty troll club and he has to say things like that to stay in the club and earn troll merit badges.
8 months ago