whilst i applaud you in your quest to ensure the safety of the child - i must agree with some of the others - you went about it in the wrong way.
you should have just told him the score and left it at that - you cannot force him do anything, and laying on the "rambo/tough guy" speak, just because he "answered you back" and asked you, what i think is a very reasonable question and what most of us would have wondered in the same situation, whether or not you are a "copper".
who do you think you are that a grown man, when confronted in the street by a stranger ranting at him, would not answer you back!?
and i agree - why would anyone not think you may stab them? how you have misread bednobs comment on this as a personal attack is ridiculous!
you are a complete stranger! you may know you have no intention of stabbing anyone, but no-one else does!
or do you think that you don't "look" like a stabber so no-one should be at all wary of you?
i understand your anger and your wish to help a child, and i commend you for being brave enough to tackle the situation - but yes, you went over the top, and to be honest if someone carried on like that to me - for whatever reason, i'd have said a lot worse than he did!
incidentally, would you have said the same thing before the laws came in?
i notice a lot of people can only see the bad in things if there is a law about it.
hardly anyone ever complained about mobiles in cars - until the law came in - and then it was self righteous indignance all the way, and same with many other things.