A few facts......
a) Some people just have a problem with authority. Some posters on this thread show classic symptoms. Most crew don't weild their authority in a "power trip" way but they have authority.
b) Checking boarding cards will have some type of revenue protection reasoning attached to it. However, like everything, safety and security is the primary reason. Someone on my aircraft who is not authorised to be so is a security risk. I don't know whether they are a terrorist, a stow away or a lost passenger therefore they are a risk to myself, my fellow crew members and my passengers.
You will therefore find that if unauthorised passengers are discovered inflight, procedure will takeover because it is deemed a security risk.
c) It can be frustrating having to show boarding cards at the aircraft door aswell but just keep them to hand.
Boarding card for boarding?? Whatever next? They'll be asking for money in Tesco.
The truth is many airports don't have airbridge equipment and therefore it is very easy to attempt to board another aircraft.
Who are left to deal with this? Cabin crew and to a lesser extent, flight crew.
d)Going through the airport these days is sometimes a nightmare. If you don't like it though then the choice is simple, don't fly. The airport experience isn't as good as what it once was but we do have the terrorists to blame for that. Therefore you shouldn't be rude to cabin crew, nor is it acceptable to be so when they simply ask to see your boarding card for a "final cabin crew like to be sure check" and more importantly for the passenger, to make sure you are on the right flight. Why? Because the passenger seldom accepts blame for boarding the wrong flight.
e) Some cabin crew can be stand offish.........yes. Some passengers can be ************************************** yes. That is human nature as much as i hate it.