I like to act friendly to people in those situations, and just talk to them like they're my friend. Joke around, and act like everything's cool. Because they're being an asshole to me and in return I'm being friendly, they get confused, and will either stop.. or get angry and hit me. In which case I'd grab the nearest object (Hey, I'm a small guy) and proceed to shove it down their throat. I gave them more than a chance.