Actually ends up sorta happy I Guess....
Truean, as usual sorry about what you deal with in your line of work. My buddy who works in nursing is dealing with a similar level of jadedness with his clients; on multiple occasions he's shared stories about being forced to put up with Users who feign pain and disability every day in order to legally obtain drugs, and vegge out on the State's dime, while other people are turned away from or avoid seeking treatment because they lack the very medical coverage these patients are abusing.
Just remember that there's some kind of hurt that has these people backed into a corner... something they're trying to avoid dealing with, be it shame or knowledge of their guilt or whatever... that's driving them to treat you and your organization like they do. The people undernieth their issues are still good people, but they're made mean (in the "small-minded/ignoble" sense) by their circumstances. Maybe that will bring you some solace.
In any case, that anecdote at the end was kinda great. There's a time and a place for politeness... don't be afraid to set it aside when you need to. A rule of thumb I learned from a man wiser than me: If you find yourself angry at someone, think about whether you want to improve your relationship with this person, or don't care about your relationship with this person. In the former case (say because you'll have to deal with this person in the long-term) don't hesitate to call them on their bullshit, and if you can offer them an alternative; say it with the intention of making your interactions with them better. In the later case (say because you'll never see this person again, or otherwise have no interest in knowing them any better) just let them and their problems roll around you, and disappear into the past.