Julius Caesar 1.1 Double Meaning: "being out"

The transcript discusses a cobbler's seemingly irritated response, which carries a double meaning. On one hand, it sounds like a threat to fix someone's attitude, while on the other, it offers to repair worn-out shoes. The cobbler uses the expression 'out at heel' to cleverly disguise his offer, making it sound both rude and helpful.

What is the significance of the cobbler offering to mend Marolis's shoe?

How does the cobbler disguise his rudeness in his offer?