I do agree with what you say Paul, but I think the problem here lies in the fact that the fountain will now have to be cleaned out which costs money - tax payers money - and possibly punishing him will make other kids realise that they can't get away with damaging public property.
With regard to the recent revelations about what the police can turn a blind eye to, personally, although I would hate to see any gross indecency taking place (specially where kids can see) I have never in all my years seen anyone having sex in an open place, or in a toilet, in broad daylight!
When my son worked in the library he saw a man "doing his own thing" whilst using a computer there. When the police were called they couldn't do anything because they didn't catch him doing it. So what is the answer? Goodness only knows!