I used to be a Christian but I can't remember how the free will argument actually works. As a human, if I could stop someone doing something awful to a child, I would. Furthermore, if I knew someone had witnessed a rape they could have stopped I wouldn't think that person had acted morally. I fully expect people to intervene where they can to prevent bad things happening. If they said 'I don't want to affect their free will' I would find that deeply offensive. How come Christians find this logic acceptable?