I think the guy is stupid, but I’m willing to give a professor, individually, some leeway here. If they can ban cell phones, gum chewing, even talking in their classroom, then they can probably ban firearms. The class is a voluntary association between the professor and the students, and if the students don’t like the rules he sets, they don’t have to take his class.
To be fair to his students, he should probably announce this on the first day of class, so anyone who wants to drop his class can do it without penalty if they don’t like the policy.
If the perfesser PAID for the room I might agree. He doesn’t. The taxpayers do. End of story. If he does not want to be in a place where free people can exercise their rights he should go elsewhere.