Why do abusive trainers persist?

I have a consultation on Tuesday with a woman whose four month old dog was hanged, slapped, an alpha rolled by a dog trainer in a nearby town. She stayed till the end of the class and isn't going back. Personally, I would have launched on this... guy before the dog got off the ground, and when he was finally able to get up, he would have found me and my dog in front of the dust getting out of there! This guy advertises himself as a "positive" trainer. Were this true, none of the above approaches would have been employed. Ah, he also REQUIRES the use of prong collars on all dogs attending his classes. I would venture to guess that he is also abusive to the humans in his household, wonder if they sport prongs? Please check out the attached link and see what the experts and other positive trainers who are using operant and classical conditioning instead of compulsion to train really think of the latest leader of this outdated mentality pack.