[larrys]

"It is no less wrong to hit your kid than to hit your spouse."

Presumably a spouse has more intelligence, maturity, and common sense than a child and is a peer (equal) that you can speak to and don't have to resort to "spanking" or much worse.

[gnaritas]

A person who can't outsmart a child has no business raising one. Words work just as effectively on children when applied consistently.