You cannot "parse" proverbs to your liking, they have usus. No one would say that to a smiling person. I believe it's ever being said now only to children, who

You cannot "parse" proverbs to your liking, they have usus. No one would say that to a smiling person. I believe it's ever being said now only to children, who burst with laughter after whispering around or on hearing the word "toilet". And clearly this proverb is irrelevant to the topic, since we "parse" US smiles as happening for an obvious reason - social convention.