Althugh not an aggressive exchange, it was highly amusing.
Queuing in my local book shop, there was a group of, I assume, exchange students, behind me, talking in German and laughing among themselves. The one of them said something in a loud voice, directed at the lady assistant and his friends all laughed. The lady said something to him, also in German, and he blushed bright red, and his friends did as well.
When I got to the counter, I asked her what the exchange had been. She told me that, imaginging he was securfe in using a foreign language, he had said to his friends, 'I wish the old bag on the counter would get a bloody move on so we can get out of here!' She replied, also in German 'The old bag is going as fast as she can and appreciates your patience and courtesy in waiting your turn.'
It was a priceless moment - young people can be taught to think about their actions, if the circumstances are right.