I'm pretty open. You can ask me almost anything and I won't get all huffy about it, so impertinence doesn't really come into it. But...
A couple of years ago I bought some new clothes and the guy on the counter said, "Do you have your senior's card?" I tried my best to look huffy and growled at him, "What makes you think I'm old enough to have a senior's card?" And he said, "You look just like my father." Gave me a good laugh.
On the other hand I was in Cairns (near the Great Barrier Reef) a while back and heard and heard an elderly American tourist complaining to his wife, "These are the most uncourteous people I've ever met." I would have stopped and explained that we're really "discourteous" but I doubt that it would have helped, so I kept walking. I guess he'd been into a shop where some pimply faced kid had called him "mate".