Question

Why doesn't Taplow calls Crocker Harris a sadist?

Answer 1

Sadist is a person who takes pleasure in inflicting pain to others; Crocker Harris did not give any sort of physical or mental pain to anyone. He just kept a safe distant from his students and maintained a professional relationship with his students and colleagues. Every student knew he was strict, but not sadist.  

Answer 2

Taplow knows that a sadist gets pleasure from inflicting pain. But, according to Taplow, Mr. Crocker Harris is not a sadist because he rarely displays any human emotions. Instead, Taplow finds Mr. Crocker Harris to be shrunken from within as his emotions are almost dead. He finds it strange how Mr. Harris disliked to be liked.