Having worked airline customer service and having helped many jumpseaters, my 'professional' opinion on the matter is that its probably not a matter of jealousy or a vendetta against pilots, but just a general lack of professionalism in the customer service world. The job pays a meager hourly wage and anyone who can produce clean peepee can get the job, which obviously opens the door to a lot of people who most definitely do not hold professionalism and courtesy in a high regard.
Of course there are good agents and not so good agents. As for myself, I always made every effort to take care of all jumpseaters (and if I may admit...I probably took better care of the jumpseaters than I did my own paying passengers!

), but you know what? It was a much more rewarding interaction. Ended up being on a first name basis with many of the regulars and knew how the family was doing, etc. It completely baffles me as to why people who work for the same company but in a different department would be so happy to **** on someone from the same team at the drop of a hat. Being an amateur pilot with intentions of finding a way to get paid to do it, I may be a bit biased, but I digress.
But what is a testament to the pilot group is the resolve that you guys have to not stoop down to the level of the butthead agents. I can probably count on one hand the number of jumpseating pilots that I've encountered that were legitimately acting out of line, as compared to the numerous agents. (flight attendants though.....)
Just a general lack of professionalism through out the customer service area. Disappointing.