How does Benvolio show himself to be a reasoning man?

Benvolio is a peacemaker. In act 3 sc 1 Benvolio senses a fight in the air. It is hot outside and the blood boils on in both the Capulet boys and the Montague boys. Benvolio appeals to Mercutio to call it a day:

I pray thee, good Mercutio, let’s retire.
The day is hot; the Capulets, abroad;
And if we meet we shall not ’scape a brawl,
For now, these hot days, is the mad blood stirring.