"That's no different than saying 'shut up,' and you always say we aren't allowed to say 'shut up'!"
"Then stop saying it and listen to me."
"Why are you allowed to say it?"
"I didn't say it."
"But you said-"
"I know what I said. And saying 'keep your mouth shut when I am talking to you' is not the same as saying 'shut up.' If I wanted to say 'shut up,' I would. But I don't, because I think it is rude, and I don't want to be rude to you."
"So telling me to keep my mouth shut while you are talking isn't rude?"
"So I could say it to Sarah and not get in trouble."
"Oh no. You'd get in trouble."
"Because that would be different. That would be rude."