I think it is inappropriate to call that a “pornstache”. That is clearly a “moleststache” variant, and the instructor should have been trained to recognize it.
That said, insulting an Arab man’s mustache would be considered “fightin’ words” since to his perception, it is a symbol of his virility and manhood. Military instructors who deal with foreign students are given training exactly on these things.
Reason to shoot up the place? No. Full stop. The instructor hurt his feelings, he didn’t spark a massacre.
My son’s nickname for 4 years in the Navy was BUNDY as in Al Bundy’s Married With Children.
You’ve just given the best reason muslims should not be in any western country. Full stop. We are culturally incompatible.