I have had ID90s for all my life.
I have been son of airline staff since born and then airline staff myself.
I have experienced bad and good staff travellers, both when I was a passenger or when I was working.
It is all down to common sense and respect for other people.
The basic assumption is that all concessions are a privilege and you are not entitled to the same rights as commercial passengers.
Anytime I have seen staff complaining because of long stand-by lists, missed flights, delays, setas,etc I felt sorry for the entire human kind.
This behaviour is unacceptable and they should be banned straight away whatever the rank.
I have even witnessed the following, you will not believe this:
a flight on a B777 was diverted to NewFoundland due to a medical case, a passenger needed urgent medical attention due to hearth attack.
Well, a passenger started complaining (he had an important meeting) with the CSD and the Captain had to intervene: this is another case of human madness. Nothing to do with staff in this case, it is just that some people are simply idiots, whatever the job they do.