I have little doubt that this kid was being a little turd, and a lot of parents don't have rules, discipline, or proper parenting at home. As a result some kids just act awful. But I can't watch this video and think of a single justification for the teacher acting this way.
Let's say the kid told the teacher to f#&k off, threw a desk across the room, and mooned the class before casually strolling into the hallway. There are a lot of problems that the teacher, the school, and the family will need to address. But physically accosting a 6 year old? No way. You might want to, but you just can't.
Even if the kid had a weapon or was being dangerous, it might be necessary to wrap him up to prevent him from hurting others, but even if so, there was no one else around to possibly be harmed by the kid, and the response to someone with a weapon is not to grab their face or shake them.
I work in child protective services and work with unruly children of all ages, and unruly parents of all ages. You can't lay a hand on anyone, unless you are truly defending yoursefl and can't otherwise get away. Neither can teachers. There are other ways to deal with problems, and if you can't resolve it without getting physical, that's what police are for. Otherwise you set up a plan for dealing with the issue.
And for those of you saying that you would get violent with any teacher who did this to your kid, that's not the answer either. That's the same sort of attitude that this teacher adopted. Use physical violence to protect yourself or your family, fine, but as retribution, punching the teacher in the face o rusing turkey basters as torture (okay, I am honestly interested in what BRI had in mind!) does not solve anything or teach the lesson that the initial physical alteraction was wrong.
If a teacher did this to my child, there would be hell to pay in terms of the school enforcing (or revising) their policies or else face a lawsuit and/or a PR bloodbath. And that's what's happening here, it looks like. This teacher is going to lose her job, no doubt, and that's fine. But as a parent, I would also be asking the kid how this all started and address his own behaviors and impose (nonviolent) consequences.