I, too, have seen the type of person DrHowser describes. Besides the embarrassment they cause to everyone around them, anyone with a room-temperature IQ should know that ticking off a person who has the power to do (or not do) something for you is not a constructive strategy.

I'm glad the agents know it's not personal. Being cut off in traffic isn't personal either - but it can still make your blood boil. It can be tough to stand there and take it.

I once got an upgrade just for being next in line after a series of these and taking care of business with a smile. (There were weather delays and we all had to be rebooked.) The agent was quite candid about why I got it - she appreciated the relief!