I'm ashamed of you

"I'm ashamed of you," the mother said. "Fighting with your best friend is a terrible thing to do!"

"He threw a rock at me!" the boy said. "So I threw one at him."

The mother stated emphatically, "When he threw a rock at you, you should have come to me."

The boy quickly replied, "What good would that have done? My aim is much better than yours."