I would probably just walk away, shaking my head. People make their own karma.

My younger son, on the other hand, would provoke the guy, begin lambasting him for being an idiot and a self-centered asshole in hopes that the guy would take a swing at him so he could make him bleed a little (or a lot). I'm not saying my son is right, but more often than not being verbally confronted by someone big and tough in this land of pushy milquetoasts puts enough of a scare into them to make them reconsider their selfishness. Of course, you have to be the sort of person able to physically back himself up. If the person confronted simply walks away, that ends it. No slashing the tires, no keying the paint job. A verbal lambasting is usually as far as it ever goes.

With a woman it's a bit different. No physical confrontation offered or even implied. But a few choice derogatory, non-politically correct words about her actions or her person (ever notice how pushy women are usually obese and have yappy little dogs in the car?) will give her a nice adrenaline shot and some food for further rumination.

And if you're the woman doing the lambasting to a man, you can pretty much say whatever you want and the man won't physically attack. If he does, he goes to jail and he knows it. A woman cussing out another woman might end in a cat fight. I'm no judge of that sort of situation so you have to use your own judgement.