Well, tell your girlfriend "Welcome to the Real World!". EVERYONE who has to deal with the public encounters a few "belligerent, hostile people"- but most of us don't leap to the assumption that ALL the folks we deal with professionally are going to be major pains in the butt! Also, the open contempt (shown by a few "flight attendants" I have met) for the travelling public is counterproductive, at best.
The attitude improves a whole lot when I travel in First-Class- are there perhaps some "class" prejudices at work here? Or is it just the "Us vs Them" mentality that you alluded to previously? (By the way, I have never gone out of my way to give any airline folks a hard time- I don't expect much from them, so I don't ask for much. Bring me my one drink and my little bag of gerbil snacks and leave me alone).