The thing is, that rapists thing was one case. Rehabilitation generally works, you just done hear about the success stories, because they "don't make good news"...
Call me naive (I am, after all, the Naivest Cynic you'll ever meet
), but I am generally inclined towards the idea of giving people a second chance. Should ten rapists who could be rehabilitated be killed just because one couldn't? I just don't think that is right. How could you know whether or not rehabilitation would work on a person if you just kill them, without giving them a chance?