Well I suspect the traveller, who doesn't sound too experienced, may have contributed to the problem... but why is it that airline employees adopt a hostile, nasty attitude towards customers? It happens time and time again. The alternative would have been for the rep to say
" I am so sorry, but unfortunately I have already done the loading sheets and signed off on the paperwork and the door has been closed. I can understand how frustrating that is for you, but it would cause a delay and may result in the aircraft missing it's slot if we allow you to board. Let me see if I can find someone to help you".
It is the hosility that is so hard to take.
There, is that any better PHX...?