The teacher is obviously terrible at his job. The whole point of symbols is that they have greater meaning than they have intrinsically as objects. Looks like this teacher finally learned this lesson the hard way.
I would have less of a problem with him stomping on the flag and saying "You are probably getting angry, and while I'm not stomping on America, you see me stomping on a symbol of America. If I was stomping on some other piece of cloth, it probably wouldn't bother you. This is how objects used as symbols are imbued with more meaning than what they possess as a physical object."
Unfortunately this man is an idiot and not fit to be a teacher.
If I appear to be ignoring your posts, it's probably because you are on my ignore list.