Child: Shut your mouth please.
Me: Hey! You don't say that. That's really rude. Don't say that again.
Child: But I said "please."
Me: "Please" doesn't negate the rudeness. "Shut your mouth" is really rude.
Child: But I said "please!"
Me: I can say, "Please know you're really ugly." That's still rude!
Child: Hey, I'm not ugly!