It is funny when you think about it. When man was first created, we had no clothes. Everyone walked around naked. No one was ashamed of their nakedness. Humans did where clothes, but the reason they wore them was to stay warm, not because they were embarrassed of their nudity. Over time nakedness became shameful. Maybe it is because people wore clothes more and more, so seeing a naked body became uncommon and uncomfortable.
The real source comes from the Puritan values that serve as the basis of philosophy for Americans. I am sure the other parts of the world has something similar. Puritans were very strict about sexual behavior. Two books that do a good job of covering Puritanism are The Scarlett Letter and Tess of the D'urbervilles. In those books the women are held to a standard. In Tess of the D'urbervilles, Angel immediately abandons Tess when he finds out she is not a virgin. Point being that reproductive organs are bad to be seen because they imply sex. If everyone walked around naked would sex rates go up? I would not be surprised if they did. I think it is interesting how humans start off carefree and naked, but overtime become strict and embarrassed.
I am not saying everybody should be naked all the time. By now society has beaten into us that nakedness is bad for so long. It might seem hypocritical, but I would defiantly not strip naked publicly. However, for movies I think it should be different. I can understand not wanting kids to reenact sexual behavior, but flashing a breast for two seconds will not make children perverted. It is human nature to think about sex anyway. Our main priorities as a species is to survive and reproduce. The rating system should either give equally strict ratings to violence or become less strict with nudity, so it balances out.
