Guy reacted with ambiguous behavior after experiencing frustration, why?

So basically I was talking with this girl and she mentioned that my intuitive guy friends friend which is "serious" lol (which was yonder to us within plain view) is awesome looking. We both looked over at him and he just happened to look at us with a confused look. Then we just started talking about something else.

Later on, my guy friend came up to me with a angry bird look on his face, acted hostile, and suggested he wasn't okay with being made fun of. He then stepped forward, as to seemingly establish a scare.

After his reactive aggression, is it ever worth saying anything nice to him?

And why do you think he was so ambiguous about being glanced at?