When I picked my mom up from the airport recently, she told me on her flight up the FA seemed to single her out specifically. She said she had absolutely no idea what she did, assumes maybe her resting face must've looked mean and the FA went and was rude and passive aggressive to her the entire flight. She was in first and said she doesn't expect any sort of special treatment, but couldn't understand why he made her feel like such a bad person when he treated everyone else with a smile.
Hearing it upset me because she's one of the nicest people ever and doesn't ever cause a fuss.
But regardless of how bad someone's day is, it is their JOB. They are providing a service, and if they decide to be rude or give attitude, then they can't expect to not receive the same in return. I'm a super passive aggressive person, so had I been with my mom on that flight, I would have ended up calling the FA out.