hmmm? Say again Carlitos, I can't understand what you have meant.
Generally I could never understand questions like this one. If we are for equality, then the rule goes both ways for boy and girls. Other words you either can hit both, or you can't hit anyone, for fairness and equality.
It looks like this is a left over of traditional patriarchal families, when man was a head and ruler, and woman and kids were a property. Most man were slapping or even bitting wifes on many occasions. It is unthinkable now in western world, though practiced heavily still in third world, even culminating in "honor killings".
I wonder who gets slapped more these days in western hemisphere? We know that women are more emotional than men...