Why is female sexuality looked down upon?

Many people look down on girls and call them sluts or imply that they are easy. Even if they are not. It seems girls are not allowed socially to express their sexual desires. One example is that if a guy gets a lot of girls he is called a player, looked up to, and has increased social value. A girl with multiple "guy friends" is looked down on and called a slut, skank, a whore. Girls actually enjoy sex more that guys do and have some pretty freaky sexual fantasies. If you don't believe me, read the book "my secret garden."

I'm a guy and have noticed this, and find it odd that so many people condemn girls so easily.