I do understand that it is not very nice to see a stream of urine in the street, and I think the least a decent parent should do, when coping with a child who is "taken short", is make them pee in the gutter so that folk don't have to walk in it. If the child is older than about three they should have learned to manage their bladder. I also think that many people in the UK feel that the public streets belong to everybody, and that nobody has the right to lecture anyone else about what they do, as long as it is not illegal. Hackles can easily be raised.