I personally feel that you make your school look even worse by spending so much of your post trashing the former teacher. It's no different than the hagwan owner who blackballs his former teachers. I've seen it so many times.
As a prospective teacher, I would be more concerned with the condition of the school than with the quality of a former teacher. If your best defense is to attack the messenger, then I think you really don't have much of a defense. Besides, I wouldn't want to work somewhere where I could be trashed on the internet if I was fired.