He should have taken the phone, hung it up, handed it back and asked the student to leave and not return. He only showed that he doesn't have control of the classroom.
Part of me wants to say that he was in line, but the physical violence he demonstrated (albeit towards an inanimate object) bothers me a tad. I probably would have simply confiscated the phone, met with the student after class to ascertain that there wasn't some life-or-death reason for the call and (if not) thrown it out or submerged it in water. Mildest case, I might have retained it until the end of the semestre and required an essay on manners and etiquette, along with an apology to be read to the entire class.
This is presuming, of course, the class policy regarding cellphones had been clearly stated.
I think he was right to take the phone, but not to smash it so violently. But then, I have no tolerance for crap like that, especially when it comes to cellphones.
It was maybe out of line, but I can understand why he would do it.
Goodness!! Just imagine what that teacher would do to the student who filmed him hitting a student, and posted it online!
I remember in grade school there was one teacher who apparently would throw chairs and desks when he got mad. I remember being so glad not to get in his class!
Like many other commenters, I think what he did was inappropriate. Take the phone away, send the student out, etc. but not break it. I know it's not likely, but what if it was an emergency and a parent calling? Can you imagine how that would have gone over?