As MT has already pointed out, it's clearly a joke response - an attempt to wind the Americans up, if you like. It clearly was terribly successful - not only did the bottle thrower (or "litterbug", as I think we can agree to refer to him) fall for it, but so did his local press and most of the first 5 or 6 American posters in this thread.
I particularly enjoyed the disparaging "shakehead" smilies. Heh. Nothing beats winding the colonials up.