Yeah, it sounds like pure fearmongering to me. If your waiter or flight attendant is grumpy, are you going to lose your shit and act belligerent, or can you just chill and handle the situation maturely? This will never happen to 99.9999999% of reasonable people who know how to behave in public. Yet 99.999999% of service industry workers are guaranteed to be treated like trash by belligerent customers on a frequent basis.