I don't remember where I read it, or maybe saw it in a movie, but the conversation that springs to mind is, after a guy has asked a waitress out,
"Sorry, I don't date customers."
"I accept your rejection but not your reason."
"Whuh?"
"You say you won't go out with me because you don't date customers, but I know for a fact that there exists at least one man out there that you can name right now that you would break that rule for. Therefor, you don't have a rule against dating customers, you just don't consider me attractive enough a customer to go out with."
".... yeah."