According to the nonfiction book, Let Me Hear Your Voice, what is the controversy about behavioral modification therapy?

Behavior modification therapy is controversial because many who know about it see the process as cruel, particularly in regard to the negative reinforcement. In some cases, negative reinforcement takes the form of physical punishment, which can be necessary to stop self-destructive behaviors. However, according to Bernard Rimland, those individuals who criticize the program as cruel do not understand modern techniques.