Win more with sugar!
Dealing with upset and rude passengers is a daily challenge for flight attendants, myself included. Kill them with kindness works almost 99% of the time for me. I start with "bless your heart, you must...." along with a big smile seems to take the wind out of their sails. Most of the time they just want to feel that your on their side. I had a woman on my flight who had her bag on her lap....I very kindly told her that the bag needed to go under her seat. Her response? "Oh shut up, shut up, shut up." I smiled and said "bless your heart you must be just miserable" then walked away. She was literally speechless. It also works well with grumpy coworkers.