Sadism is not an infectious disease that strikes a person all of a sudden. It has a long prehistory in childhood and always originates in the desperate fantasies of a child who is searching for a way out of a hopeless situation.
The reason why parents mistreat their children has less to do with character and temperament than with the fact that they were mistreated themselves and were not permitted to defend themselves.
Wherever I look, I see signs of the commandment to honor one's parents and nowhere of a commandment that calls for the respect of a child.