I've become somewhat passive aggressive because of people like this. As an old fart, one of the advantages is that I can push back a little, and if my manager disagress, I stand pat and refuse to back down. I never stop being polite and professional, but I don't hesitate to school the unreasonable clients in what is and is not possible to do for them.
On a lighter note, go here for some relatable lulz: http://notalwaysright.com/
On a lighter note, go here for some relatable lulz: http://notalwaysright.com/