Final answer:
In Act III, Mercutio accuses Benvolio of being hotheaded in a humorous exchange, despite Benvolio being known as a peacekeeper.
Step-by-step explanation:
In Act III of Romeo and Juliet, Mercutio jokingly accuses Benvolio of being hotheaded. Despite Benvolio's reputation for being a peacekeeper, Mercutio humorously claims that Benvolio is quick to anger and start fights over trivial matters. This exchange happens in Act III, Scene 1, where Mercutio teases Benvolio about how he would quarrel with a man for cracking nuts for no other reason than because he has hazel eyes, among other frivolous reasons.