"We do not train to be merciful here. Mercy is for the weak. Here, in the streets, in competition: A man confronts you, he is the enemy. An enemy deserves no mercy."

~ John Kreese

There's no such thing as a bad student. Only bad teacher. Teacher say, student do. This passage explained by Mr. Miyagi to Daniel after getting pummeled by Kreese's students could not be more true than in the case of John Kreese, sensei of the Cobra Kai dojo.

Young impressionable kids need strong role models. Not physically, but mentally. Where there is violence involved, the role model must be docile because balance is key. Violence is always hard, so teacher must be soft. The result = student of balance.