If he really did rape the girl (and it certanly seems so) then I agree with you. Apart from the "throw the key away" thing. I agree with the author when she says " after one is convicted of a crime, one is sentenced accordingly, then given a chance to start anew once that sentence has been served". If that's not the case than we might as well shoot him. Saves us the costs of keeping him alive, you know.
Whoever can see through all fear will always be safe.