Recently, I read a book written by Heather Poole, a flight attendant with over fifteen years of experience. In her recent book, Cruising Attitude, she writes of an incident she observed involving a fellow flight attendant and an unruly passenger. The passenger was belligerent and rude and he told the flight attendant to "fuck off" when she asked him to sit down and buckle up. After unsuccessfully trying to reason with the angry man, the flight attendant leaned over and whispered "Fuck you." in the man's ear. He went ballistic. She called the cops and had him arrested. She waved goodbye while the man was dragged off the plane in handcuffs.
My point in relating this anecdote is not that I think you should resort to bullbaiting difficult people. It's more that when you're in a potentially embarrassing situation with an adult who threatens you with bad behavior in public, you should just go ahead and let them act out. I guarantee if the person freaks out, it won't be you who is considered an asshole, it'll be the person acting out. A public meltdown is embarrassing, for sure, but you can use it to your advantage, especially if you have a cell phone that makes movies. Stay calm, though. You might even want to discreetly distance yourself and watch it as if you were an uninvolved, objective person.
Here's the thing. Adults are responsible for their own behavior. You don't have any control over anyone else's behavior but your own. While it can be embarrassing or humiliating to be with someone who acts out in public, you have a choice as to whether or not you have to put up with it. And someone who threatens to act out in public in an attempt to control you is someone you should allow to go ahead and hang themselves by their own actions. It may seem like you're dying a thousand deaths when they act like jerks, but trust me, you're not the one that others think is a loser.