He did same thing which normal man should do. How can a normal husband can keep cool when he sees his wife cheating him (at least its his assumptions as wife not cleared anything to him and hiding her relation / meetings with other man).
All his questions to Bhai was perfect but Bhai to gadha nikla ...apne dil ki baat bol bhi nahi paya...
The punch was solid...bhai ki hawa nikal gayi... Although he was knowing that he could not hit back RK (power hai kaha gadhe me) ...to impress Madhu he just act to hit back but then realize that it will be better not to hit back so when Madhu's signaled him not to hit back he stopped immediately and saved himself and even glorify himself in Madhu's view.
He is BIG shame on underworld.