I'm always amazed when I hear stories about that level of melodrama regarding food. Even though I've seen and experienced it, it's almost surreal how ugly people become. I've primarily worked food service since high school, I have dozens of really hilarious stories about the people who turn in to shitty, terrible monsters when it comes to their caloric intake.
But it's not even the huge outbursts that get to me. Those can be funny due to how absolutely ridiculous they are. The more subtle dicks, especially the regulars of which there are a few at my current place, who just want to take the shit out of you because the service you offer isn't worthy enough of any respect, are what really get to me haha.
Because I have to work five days a week and I know it's likely I'm going to run in to this one specific old fart who nitpicks anything he sees me or one of the waitresses do, and we don't have any way to tell him to suck it because he's a paying customer. One of the girls came in the back once crying because of some really rude shit he said to her, we were really busy and she kept forgetting to bring some coffee to his table while she was rushing around doing a dozen other things. He got up while she was taking someone else's order and interrupted her to berate her and call her something like a fat, dumb bitch. What's worse was our manager came out and apologized to him and comped his coffee so you know he thought he was right in upsetting the waitress that badly.
Same guy has also wandered back in to the kitchen area to tell cooks to hurry up, which was way beyond my comprehension. He just has this need to intimidate and harass everyone at his "favorite restaurant", but at least he tips I guess.