It's rude to tell someone to shut up.
Bobby is watching a movie at a movie theater and a man behind him begins talking a bit loudly.
Bobby wants to get the man to stop talking.
Bobby turns around and asks the man if he could please stop talking while the movie is on.
Bobby turns around and rudely tells the man that he need to shut up so everyone can hear.
The man feels embarrassed for disturbing Bobby and immediately goes quiet for the rest of the film.
The man behind Bobby gets angry and escalates the scene by trying to start a fight.