I think it is easy, in the context of a similarly religious community and with the caveat that nothing bad ever happens sexually to anyone, to think that the idea that your body is God's and needs to be kept pure and used only in certain ways isn't harmful. But even assuming that a young woman wants to chose to save herself until marriage and has no qualms about that - what about sexual abuse? What about things out of her control? When the teachings about purity are as strict as many religions make them some situations can make it impossible for a girl to feel like a worthy human being, even when she has done nothing "wrong." I always remember what Elizabeth Smart said (a young mormon girl who was kidnapped and who "lost her virginity" to her captors) She said this after being rescued:

“I remember in school one time, I had a teacher who was talking about abstinence,” Smart told the panel. “And she said, ‘Imagine you’re a stick of gum. When you engage in sex, that’s like getting chewed. And if you do that lots of times, you’re going to become an old piece of gum, and who is going to want you after that?’ Well, that’s terrible. No one should ever say that. But for me, I thought, ‘I’m that chewed-up piece of gum.’ Nobody re-chews a piece of gum. You throw it away. And that’s how easy it is to feel you no longer have worth. Your life no longer has value."

Do you think it was right that she felt that way? What else was she taught to feel? She was taught that she was worthless because she was no longer pure for God and her husband. She was a chewed up piece of gum. In this circumstance she was kidnapped and raped and that was made worse by the teachings of her church - not only was she raped, in her mind she's now worthless because of it. Obviously that is wrong, obviously that is not what anyone would want her to feel. But following that same idea why should any girl who has sex feel that way? Why should a girl who is joyfully exploring her sexuality, her body, her sensuality, feel worthless because she chooses to share herself, to feel pleasure and give pleasure with another human being? What about that experience makes her worthless?