I own a Coton de Tulear, a rare breed from Madaqascar, almost 2 years old. He loved everybody when I first got him, children, other dogs, anyone. Took him to an obedience class to teach him simple commands when he was little over one year. He hated the teacher and showed his teeth and snapped at her. She threw him down and held him pinned to the floor each time he showed any aggression.Happened each class when he saw this teacher. Dropped this class and waited for one with small dogs only. Same thing happened. She told me to have him neutered. I did ,but he continued with this aggressive behavior toward my grandchildren, neighbors, everybody. I am at my wits end. Any ideas?