Well he played with his penis and it felt good. Let him know thats something frowned upon in public and must be done in the confines of that bathroom, shower or his bedroom. Also you need to buy him some baby wipes.
When he gets older teach him to masterbate into condoms. That way he'll get good at putting condoms on and probably won't get a girl pregnant because of his excellent masterbation experience. This paragraph was a joke.
You really need to get your head straight on this.
Not funny, not funny at all. She is a honestly concerned mother who is looking for advice on a serious question about her son. There is no need to be rude.