This is why I have said in the past that college policies have to be changed so that students can tape any class lecture. In fact, schools should make it a policy that the schools will tape all lectures and keep them avail;able to students for one month. The students would not be allowed to sell the tapes but they could use them for study purposes. Just the knowledge that the their lectures are on file for a month would help to curb some of the propagandizing by the profs.
The selling is what's at issue here. Lectures are often considered to be the intellectual property of the professors who give them.