People shouldn’t say “thank you” when there is nothing for which to be thankful. Take, for example, the people who stand near the Wal-Mart exit only to say “thank you,” presumably for shopping at their store. But all you were doing, hypothetically, was buying some Preparation H for a very selfish reason; if anything, you owe them for providing the relief. And how are you supposed to respond? “You’re welcome”? They’re welcome for you to grace their store with your appearance? Or how about “No, thank you.” But she didn’t do anything…she just stood at the door, thanking you for…something.
So I propose that the next time such a situation arises, your reply be, “Thanks for nothing, you son of a b*tch.” That’s the American way.