Having spent the last 20 years in a high school, I believe that teacher assaulted that student. There is no circumstance where a kids words deserve a physical assault. I've been called every name in the book, threatened, had my classroom trashed including defacating and urinating in the floor (go central falcons!). I have been so mad that I couldn't speak. Never have I come close to touching a kid.
Dont get me wrong, there are definitely times I've wanted to do exactly what this dude did. But when a kid is in your classroom, it is your job to protect them and keep them safe. Not bust them in the jaw. You have to have more control.