There are some people who deal with problems by just repressing it or ignoring it. Maybe that works for them. But they should know it does not work for everyone.
It is also a sterotypical masculine response to emotion. Most guys I know tend to get uncomfortable around some emotions. They are fine with excitement, being pissed off, being angry or even a little bitter and depressed. But admiting weakness is out of the picture.
The caveat to this is that a very good guy friend is someone another guy can admit his emotions without being belittled afterwards. There may be some joking, but it is designed to make the other guy feel better. I think most of this is just common society rules or guidelines. It doesn't make it right though.
It seems to me that this guy can't relate to another person's feelings and therefore assumes the emotions are invalid. What may be intersting is to see if he feels the same if a woman was feeling it. That may tell you if he is reacting from lack of empathy or just going along with some of society's views.