What are the people doing that angers Marullus and Flavius and why does this anger them?

celebrating the victory of Caesar over poprey's sons.

By belittling Caesar's victory and reminding them of the days they used to watch and cheer for Pompey's triumphant return. He makes them feel like they are disloyal to Pompey.

I think when they are being insulted or being criticized when someone hurts or cheats when they are being ignored or when someone disagree with them when they lost something or when their wish cannot...

some people just put a bracelet on and just hit it every time they get mad

Because when the first humans sinned, they brought curses upon this world. Anger is a sign of sin. If you are looking for someone to blame for bringing anger here, blame Satan.