Children have rights too. They are their parents' responsibility, not their parents' slaves. You could try to lock them up away from the world, but such behaviour is considered cruel and monstrous, because it is. They are going to have pets and probably relatives die on them. They are going to witness violence, even if just in sports. They are going to stumble across discarded porn magazines in the park. They are going to see R-rated movies and M-rated games at a friend's house. They are going to talk about disgusting things with their friends. They might try drugs and alcohol. Most of us went through this growing up. Most of us did not end up hopeless junkies, hardened criminals, or sexual predators.
Go back and watch some PG-rated movies from the 80s, like Goonies, Gremlins, Ferris Bueller's Day Off, or Adventures in Babysitting, and tell me if those movies would get a PG-rating today. Am I and every kid from my high school scarred for life because we played Mortal Kombat in the arcade when we were 14?
So trying to protect your children from every bad thing in the world, is just not realistic. Raising them in a loving and supportive home with values, wisdom and integrity so they have some idea how to react when they encounter the evils in the world is a better strategy. Don't shelter your children, empower them. They're not as weak as people seem to think. They used to be expected to do the most brutal labour [http://www.cracked.com/article_18565_the-6-worst-jobs-ever-were-done-by-children.html].