Of course he is going to be frustrated and frankly, Sid deserved that punch. He wasn't acting mahaan after all. He stood back and just waited for his wife to do the job and THEN he spoke up! He must have thought that he has backing from Riddhima now so he suddenly develops the guts to speak up! Why now Sid??
Sorry Armaan. Not everyone is as clean hearted as you are!
Though I am hating Riddhima, at least she shows some guilt in front of God.