"Girls shouldn't read big books"

"My customers often annoy me. They often make me mad, and often I think they are idiots.
However, they seldom make me want to physically assault them.
Today, though, I came very close to hitting someone.

I work at a bookstore. I was cashiering today when a woman and her two kids (a boy and a girl, both somewhere between 13-15) came up to the register. The mom was buying 2 celeb gossip magazines, and the boy put down a book. The girl then walked up and set down the newest volume of the Sisterhood of the Traveling Pants series.

The mom says "You can't buy that."

Girl: Why?
Mom: Because it's too big.
Girl: [Brother] is buying a book that big. It's not very expensive.
Mom: [Brother] is a boy. You're a girl. And girls shouldn't read big books like that. It's too thick. Boys don't like girls who read thick books. You want boys to like you, don't you?

The girl went and put the book away.

Reading it, this doesn't sound like much. And I suppose it -wasn't- that big of a deal. But I can't express the -tone- this woman used, nor the expression on her daughters face when she went to put the book away. I had to actually walk away from the register, and into the back room to avoid saying something. Still, little or not, it upset me a lot. More than just about anything I've experienced in customer service."

Posted at this website, along with six pages of comments from readers (you can guess the tone of the comments...)