Deedaa
I think you are so right!
A couple of weeks ago, while at my house, my young GD (5) started being really rude to all of us, including me, when not allowed to continue doing what she wanted (it was someone else's turn!).
Usually, I leave all disciplining to her parents when they are present, but I could see that they were at their wits end and didn't know what to do.
I was so angry, and made a snap decision to act.
I marched her up the stairs and really read her the riot act, about how I would not be spoken to like that in my own home, and would not have behaviour in my own home etc. !
I could hear myself that my voice sounded totally different from normal (very different even from my usual 'cross'voice), and for once in her life, she didn't argue. She sat there open-mouthed!
My last words were, " we will go back downstair now, and you are going to behave, right?" She nodded, meekly.
Riot act over, I took her straight back downstairs and we all carried on as normal, but without the bad behaviour, all her 'attitude' gone.
Just as you said, "a brief loss of temper now and again can be quite instructive"!