If no one would attend his classes, it would send a clear message, I'd say. Or even better: when all students let him walk in to class and they all walk out, preferably without saying a word. Silence is a powerful weapon.

Edit: let me clarify my reasoning behind this. That man is absolutely a power hungry man and probably gets off on control. Leaving him in his class all in dead silence, doesn't give him any handle to gain back control. Not even a sigh when leaving that class, is a tiny sliver of control he doesn't have. He is so obsessed by that control, it needs to be total, and when people he will regard as less (because they're students), take just a tiny bit of that away, can drive him crazy. Do that with all classes he has on that university and from his perspective that will be a big loss, eventhough it looks small. It's a crack, but a good message, I think and when word gets out that students managed to do that, more people will do it. Not just as a protest, but it could be straight fun to just make someone feel like that and scratch his ego. Of course it sounds overthought, but really power hungry people can fall at the tiniest bit of disrespect. Without a word has been said. No attention, nothing. :-)