CATSA: in the few occasions in my life I have dealt with cops, I have always been polite and deferential. Usually, I have disobeyed some traffic rule and I'M SURE TO BE CONTRITE then. Otherwise, they are helping me report something which has happened to me.
Very different situation from trying to board an airplane. Police are VERY WELL TRAINED to know that you are officially innocent, even if they've just clocked you at 75 mph (130 kph).
Most screeners are polite, but a few -- I think your 10-20% estimate is not far off the mark -- use their position to work out their own inner demons. We are all considered guilty unless we are demonstratively obsequious to them.
Many former frequent flyers are now driving or doing virtual meetings in order to avoid this. Your 10-20% load of creeps means that I run into one every third flight or so (interact with at least three TSA employees per flight, times 10% azzhole ratio --).
I have a lot of business on the left coast and cannot avoid flying or will have to completely change my life. Most of my flights and security interactions are benign, because I usually put up with the crap. But the ones that go wrong go very wrong and it seems the variable each time is the control-freak gestapo attitude of the particular screener. I react to that. Please do not tell me just to suck it up and bend over. We fought a revolution and many wars to not live in that sort of country, thank you very much.
NONE OF THIS SECURITY CRAP ACTUALLY MAKES US ANY SAFER. I know most passengers are sheep and don't know anything about probabilities, but that does not mean we are all Faux News fodder. What we are talking about here is power relationships and little people in big jobs who are getting their jollies by pushing travellers around.
It is helping to kill the airlines, keep people from travel, and not doing a dam thing to stop determined terrorists.
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"We know you have a choice of airlines" ... the most important frequent-flyer words you heard this week.