Fighting Logic

A mother of a seven year old is called to school where she learns from the principal that her son had just been in a fight.
Feeling the pressure under the watchful eye of the principal she calmly says, “I’m ashamed of you Johnny. 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 the principal and told him.”
The boy quickly replied, “What good would that have done? My aim is much better than his.”