The reason the police get involved in dogging sites is because they receive complaints from the general public, i.e. tissues and discarded condoms left around the place, most of the sites are country park car parks, so they are the last thing you want to see when your going for a walk. An easy problem to resolve.
As for boy racers and window smashes, I have been in a car park with about 10 cars dogging, one boy racer comes in with is mates and they all flee, Why is this, is it because we feel we are doing something wrong. I suggest we stand up for ourselves and make sure people clean up.