Jinoru said:
Well, They don't need to be killed. Just remove the organs which bring about that kind of stimulation.
This is a horrible idea. And I will tell you why.
Our justice systems have an element of redemption in them, right? You serve your time, you're released, free man. In sex offender cases they keep an eye on you with the register, make sure you don't do it again. I'm not entirely sure I agree with this, but given that the impetus for the crimes (sexual desire) is still there it's probably worth it to stop them reoffending and screwing up some other person.
This element of redemption is pretty important, I think most people would agree. It's why we have massive rehabilitation programs.
Now, with physical castration, you completely remove the redemption aspect. Essentially, you imprison them in a full body cage for the rest of their life. At no point has the person decided to stop raping, you've just removed that option. There's been no reform on their part. It's the Clockwork Orange free-will argument again.
Now, if they request castration (as has occurred) or if they undergo chemical castration (which requires continual treatment) they are voluntarily removing the sexual-urge that made them offend. They've made the choice to change, so you get redemption.
I think the only time the death penalty is acceptable is for Saddam/Hitler type crimes against humanity. When we, as a species, can say that the person is unacceptable on our planet, please kindly leave it.