Why does Jack insist that it was the wizard that was hit and not the mother?

There were three reasons for Jack’s insistence on only the wizard being hit by the Mommy.

First, by the time Jo realized that the story does not get a logical and fair ending if the mommy is not hit back, Jack had already narrated the story. To revert his words would mean to refute the notion that whatever parents say is right. Second, for Jack to give in to Jo’s demand would mean disrespecting the elders. Jo was very young at that time and Jack believed that it was time for her to learn to respect elders and understand that whatever elders do is for their best. The third reason was that Jack, while narrating the story, unknowingly got emotionally connected with the character of the protagonist and his mother. He pictured his own mother in place of Roger Skunk’s mother and thus could not imagine his own mother being hit by anyone. Moreover, he personally considered her to have made right decisions for him.