A question about Law and castration.

Pedophiles and rapists are probably the worst of the worst scum. Although we say that raping a child is like taking away his life, we still let them get off relatively easy with short sentences.

In many States, and many (democratic) countries around the world, there is a death penalty for murderers. That is, the State can terminate the life of a person suspected of killing; despite proof that many innocent people have been killed mistakenly over the years.

My question is: if a Country or State can end a life, why can’t they castrate a rapist? Is removing testicles such a horrible thing – when in other instances they can actually kill you? Is chemical, or actual castration worse than a poison needle?

What say you?