It's frowned upon to be rude.
Zach who isn't wearing  a watch is asked by a stranger, Nick if he knows what time it is.
Zach wants to tell Nick he doesn't know the time.
Zach tells Nick that unfortunately he doesn't own a watch, so he has no idea.
Zach tells Nick that he's a moron for not seeing that he's not wearing a watch so Nick should realize that he doesn't know.
Nick tells Zach thanks anyways and continues to walk down the street.
Nick is angry that Zach responded so aggressively to such a simple question and wonders if Zach isn't mentally ill.