In all western societies I am aware of, there are laws preventing children from being exposed to sexuality* of any kind. I believe the effort of not exposing children to sexuality is not based in facts, and may actually be harmful.
There are various studies researching how children are affected through early exposure. Unfortunatly, virtually all of those studies target abuse situations, making it hard to draw conclusions about non-abuse situations.
Nevertheless, several of these studies suggest emotional abuse is far more damaging than sexual abuse. To me this suggest that it's the emotional part (being forced) of the sexual abuse is the actual damaging part, not the sexual part.*
While the above may sound like a neutral point of view, I'd like to argue that shielding children of any age is actually harmful. It perpetuates the stigma of sexuality being a dirty and undiscussable thing. It robs (young) children of the ability to discuss sexual topics, making them more susceptible to sexual abuse.
I think parents, educators, and others should allow young children to become aware that sexuality exists. We shouldn't censor 'nipple gate' and we shouldn't put internet filters on our kids computers. Instead, we should treat sexuality the same way we treat violence. We should allow children to guide their own development, help them deal with it, but steer where necessary. (With this greater freedom, more guidance might be required, though)