I am half-expecting to be told I'm being U for posting a thread of the "please validate this thing I already did!" variety...
Recently I was at St Pancras Station. There are several pianos for public use there. They're a bit knackered; one of them has a few keys that don't work.
Some kids were playing one of the pianos, about eight or nine maybe. They were having a fun trying to play different tunes. They were banging the keys quite hard. A man of maybe 55, 60, suddenly appeared and started yelling: "WHAT THE HELL DO YOU THINK YOU'RE DOING, YOU NEVER BANG A PIANO."
I went over and said I didn't think yelling at children was very nice and that these kids probably didn't have a piano at home and did he want to put them off music? He started huffing and puffing about how the pianos had to be tuned because of people messing about. I said perhaps he could have said: "Look, this is how you play a piano," and explained nicely instead of yelling. He then started yelling at me.
He then went back to sitting at a nearby cafe table glowering at anyone who went near the pianos, so I went and found a transport policeman and told him this man had been shouting at children for playing the piano and he went to have a word.
I don't think I was being U, but...