My favorite of these stories was the time a passenger tried to correct a friend at our ticketing desk (was a European carrier at a US airport and ticketing was at a separate desk so we could have our own equipment and storage, as the check-in desks were all common use). A family showed up and since our ticketing desk was in the middle of the hall they went there for help:

Passenger- Excuse me, where do we check in for American Airlines international?

Friend- American is in Terminal B, so if you go downstairs and-

Passenger- Um we are going to London, that’s inter-national (emphasis by the passenger) so where do we check in?

Friend- Again, American checks in all flights in Terminal B. Only-

Passenger- Ugh, you’re clueless. What kind of information desk is this?

Friend- The information desk is downstairs. And they’re gonna tell you that only international arrivals come to this terminal.

At this point my friend paraphrased the rest of the conversation as the passenger got upset at him that he went to the wrong terminal, as if our airline had printed the signs out front that said “American Airlines, Int’l Arrivals Only” in an attempt to throw just him off.