I've worked for BA,Air France, Lufthansa, KLM - most on franchises or partners operating on their behalf. I've worked for Europe@s largets charter operator and largest LoCo - ergo - I've been about a bit ( Big Bill's Words ).
I have found that bad temper and bad manners is not exclusive to any one situation: passengers can kick off for all sorts of reasons, the majority not remotely associated with delays.
As the cost of air travel comes down the expectation of service rises: if you travel with my company, FR, we will take you form A to B safely in a nice new airplane. Anything else you pay for.
If you go with BA or VS or BD tho you pay more and hence have a greater expectation of service: equally, if you don't get a 0.01p FR fare perhaps you have expectation of service.
It is the anticipation of some service promise which doesn't materialise that causes problems: when the "experience" begins with a check in facility manned by the cheapest bidder it is downhill from there.