Why the interaction with students is necessary for a teacher during teaching learning process?

I am sure your question have worth like gold value.Simple answer is a mother teaches her child well because her child focus his attentions to her because she always took care of his.So if a teacher abuses a student or any kind of dispute accure b/w both then student will not focus what he is saying, he will just think in his mind, that is teacher is a bloody rascal so why i listen him.So at last they promote a weak relationship.