There are I suppose many ways to have handled the situation in the article. I always feel intent is important in these type of situations. There is nothing wrong with walking away/talking down a situation, even being apologetic if you are in the wrong in a situation. As long as YOU are making the choice to back down from a potential conflict and it is not being made for you through someone imposing fear upon you. This can only be done if you have confidence in your own combative ability and choose non-violence. The old school way of dealing with this would be to get the teacher to come in as hard and as fast as he likes, deal with him and maybe gain a few Tae -Kwon - Do converts! Just thought I'd throw the cat among the pigeons!
All the best Jason T