Ha Ha Ha Go Sox!

A New York family of Yankees fans heads out one Saturday to shop for the youngest boy's birthday. While in the sports shop, the son picks up a Red Sox jersey and says to his older sister, "I've decided to become a Red Sox fan and I would like this Boston jersey for my birthday."
His big sister is outraged by this and promptly whacks him upside his head and says, "Go talk to mother!"
Off goes the little lad with the jersey in hand and finds his mother. "Mom?"
"Yes, son?"
"I've decided I'm going to be a Red Sox fan and I would like this jersey for my birthday."
The mother is outraged at this, promptly whacks him around the head and says, "Go talk to your father!"
Off he goes with the Red Sox jersey in hand and finds his father. "Dad?"
"Yes, son?"
"I've decided I'm going to be a Red Sox fan and I would like this jersey for my birthday."
The father is outraged and promptly whacks his son in the back of his head and says, "No son of mine is ever going to be seen in THAT!"
About half an hour later they're all back in the car and heading towards home. The father turns to his son and says "Son, I hope you've learned something today."
The son says, "Yes, Dad, I have."
"Good, son, what is it?"
The son replies,
"I've only been a Red Sox fan for an hour, and I already hate you Yankee bastards."