What causes Romeo and Benvolio's disagreement?

Shakespeare often used foils to show the differences between certain characters in his plays. A foil is basically two characters who juxtapose each other so the audience can see their significant disparities. In Romeo and Juliet, Romeo's cousin Benvolio (whose name even means good will or benevolence) and Tybalt are foils. While Benvolio is just a nice guy who does everything in his power to stop a fight and keep the peace, Tybalt can't draw his sword quickly enough.

The first time we meet Tybalt is in Act 1, Scene 1. Benvolio is trying to stop the servants of the Capulet and Montague houses from fighting. When Tybalt enters the scene, he attempts to fuel the fire and goad the servants. He also tries to pick a fight with Benvolio, 'Turn thee ... Look upon thy death.' Benvolio does draw his sword, but attempts to maintain the peace. Tybalt responds, 'Talk of peace? I hate the words as I hate hell, all Montagues and thee.'

The Prince of Verona eventually has to step in and break up the fight. The audience gets the sense here that Tybalt is not only an angry man but perhaps takes the feud between the Montagues and the Capulets more seriously than any other character in the play.