What answer was he expecting to get? That she just loved being slapped by her hubby because his fingers came into contact with her cheeks and aroused pleasant feelings in her? If I were in Kesar's position I would have turned around and asked him back if Pratigya were to slap him how would he feel.
He apparently thinks that women are made differently not only in physical terms but also in emotional terms. Cant blame him for it for he sees daily examples of his mother and bhabhi being whacked around by their respective husbands and not complaining. Yes, women are more tenacious and can bear with a lot but that does not mean that they are numb to pain. They feel the same pain when slapped just like their male counterparts but many take it too. Some don't and they shouldn't, especially when they are being slapped for no fault of theirs, as Pratigya was.
I guess, Krishna is feeling guilty for slapping her for he knows that he was at fault. He repeatedly keeps getting flashbacks of the slap and feel positively uncomfortable whenever he does. He is trying to justify it by seeking the views of his friends and his bhabhi but is too proud to accept their opinions. Maybe he hoped that they would say that he was not wrong in slapping her and that Pratigya should not have made a big deal of it. That, in turn, may have put his own guilty conscience at ease. However, neither his friend nor his bhabhi feel what he did was right. Nothing to assuage his male ego. I hope the guy dwells more on what people have said and takes the first steps to reform his wild behaviour.