This guy is an idiot. I couldn’t even finish the story it was so patronizingly stupid.
In answer to his question, he can shoot if someone is displaying the means and intention to kill or cause grave bodily harm to him or another. So if a student pulls out a gun and starts shooting up the class room, he can shoot that student. If a student comes into his office with a knife and starts threatening to slice his grades into the professor’s internal organs, then he can shoot. If a student gets angry because he failed a test and threatens the professor, then the professor cannot shoot unless the student displays the means to carry out the threat.
If he was half as smart as he pretends to be (being a professor and all), then he would already know this stuff.
This guys too stupid to be an idiot. He’s in a class of his own.