overheard

"There are two things I will not talk about with my students: George W. Bush, and my work."

I overheard this declaration from one professor to another. I can understand not taking Bush-bait (he's an economics prof) but I don't understand refusing to talk about one's work. I mean, isn't the reason you become a professor to share your love of a given field with basically anyone who will listen? If I were his student I would be peeved that he wouldn't discuss his work. I am baffled.