What is the ruling on a Muslim university professor using lewd and forbidden pictures and films as examples during lectures for his Muslim and non-Muslim students in a non-Muslim country?

"Education in mixed-gender schools is not permissible except out of necessity. Boycotting a teacher's lesson who presents forbidden matters is the correct and obligatory action. The teacher's excuse is worse than their sin, as their duty is to explain the dangers of such matters and the moral corruption they bring, instead of spreading evil. Let them fear Allah concerning themselves and the Muslims with them, and let them be an aid to them in reducing evil, not an aid to human and jinn devils. Let them remember His Almighty saying: 'And no soul perceives what it will earn tomorrow, and no soul perceives in what land it will die.'"