>which means child rape is a necessary part of existence?
Having free will means having the freedom to do bad, horrible things; you also have just as much freedom to do good, wonderful things. It also means having the freedom to absolutely fuck yourself over spiritually without anyone stopping or warning you. There won't be direct physical intervention from the outside, by incarnating in a place with free will you have chosen to find and forge your own path in whatever direction you choose (positive or negative) rather than follow the fenced-in, predetermined trails.