In regard to what this man did to the 4-year old girl, yes, I say put him to death. What could be the argument against it? Oh, there are plenty who say that the man is sick and needs our help, or say that putting a man to death for killing a four year old makes us no better than a country that stones a woman to death for allegedly committing adultery.
I can respect those (e.g. Tracy, Alan) who have offered up some issues with capital punishment. I don't necessarily agree with all their points, but at least I know they're not a bunch of bleeding hearts. But some of the other crap I've heard up here on the topic really falls under the category of "intellectual pornography".