But the world isn't perfect Andy. That's the whole point.
So, JJ, if humans are all born sinless, which I understand to be your POV, where does the imperfection come from? Despite all the Baron-Cohenesque attempts to explain the occurrence of evil in some way other than the original sin concept, no-one has managed to adequately explain where evil comes from.
Going round and round and round here aren't we? I have already said - was it on another thread - I can't remember now! - things have affected humans as they evolve - famine, cold, fear of being killed by a wild animal, disease, tsunamis, terror, pain, toothache - all these things affect a growing child and produce strange responses in the psyche the more the terror - the more difficult it is to grow up healthy and that's where the rot sets in. The sin in a child is from imperfection of the sins of the fathers causing mistakes and unwitting damage to the child. There are too many of us for this problem to go away. E.g. While some British attempt at bringing up children in a kinder way might all the rage for a while - some children in another country are spoilt by some other theory and so it goes round and round. It's a Forth Bridge type task isn't it?