What was Big Willy Shakes going for?
Obviously, Speed is pretty quick when it comes to clever dialogue. Instead of just coming out and saying to Valentine that love has blinded him, Speed engages his master in a dialogue that leads to him accusing Valentine of what amounts to wearing love goggles. He also points out that it wasn't so long ago that Valentine was making fun of Proteus for being in love with Julia.
Shakespeare's portrayal of Speed (and Lance) is innovative. While servants in earlier sixteenth-century plays tended to mimic the behavior of their masters, Shakespeare does something new in Two Gentlemen. In the play, Speed's attitude toward marriage and love calls attention to his master's flaws.
This is a pretty big deal because Shakespeare is one of the first playwrights to portray servants who are capable of defining the main characters. (We also want to point out that Speed's character anticipates some of Shakespeare more infamous clown figures, like Feste in Twelfth Night.)
But back to the play at hand. So Speed chides Valentine for acting so lovesick by telling him that love makes you do crazy things. Once Shakespeare coined this phrase, he couldn't get enough of it. He used it again in Henry V and The Merchant Of Venice.