Here's a purely hypothetical example that is in no way based on reality: Let's say you're at the grocery store, mentally weighing the pros and cons of potential burrito fillings. After careful debate, you pay for your two dozen tortillas and 20 cans of chili (it's beans and meat pre-mixed! Holy shit! Is there a Nobel Prize for Burrito Construction?), but as you turn to go, the cashier hands you the bag all wrong -- like kind of sideways and twisting it a little bit at the crucial hand-off point. It slips right through your fingers, and you drop it, sending chili cans rocketing in every direction and drawing the other customers' attention to your secret gastrointestinal shame. Now you're embarrassed, you're annoyed and you start wondering why he did that: Don't they have, like, bag handling classes or some shit? What is this guy, a birthday party magician at Chuck E. Cheese's; what kind of human being hands somebody a bag with a fucking wrist flourish?
No, he did that shit on purpose, and now he's just standing there -- not even thinking about helping you -- smirking and exchanging knowing looks with the other customers. He's an asshole, is what he is. You can tell. You can spot an asshole with a mere glance; you're like the Sherlock Holmes of asshole detection, and this guy is the Moriarty of assholes. Asshole.
You should say something. "Sweet bagging, Bilbo." No, that's crap. "Nice bag handling, B ... uh ... Bagger Vance." Shit.
You know this is going to be one of those L'esprit de l'escalier moments, when you think of the perfect thing to say just 10 seconds too late. But it's not too late right now. You're pissed off, and your brain is demanding some kind of response, but you don't have a killer quip ...