I've never had my waiter be an outright asshole, but if they were (like, I'm talking harassing me or my company, etc... not just being slightly rude), then I could give two shits if they needed that money to survive.
It's a retarded system, but I'm not going to be the cheap asshole, especially on something like a date-night.
That said, I do normally write "math", where it asks you to write the total.