I bet most people on death row in countries with capital punishment - even counting only the ones on death row that actually committed the crimes they've been sentenced for, and did so while adult and of sound mind - aren't in the league of Hindley, Dahmer, Bundy and their ilk - luckily there aren't many such around.
I can't really relate to the "evil" concept that is being forwarded here. To me as an atheist I realize the "evil" term has no such clearcut meaning except as a word that various religions have chosen to use on certain people, societies, religions, acts, behaviour and so forth up through the ages. Including homosexuality, as far as I know. I certainly don't think anyone can be deemed evil or not by looking at their eyes. If it were that simple, for one thing, all those poor women who offered to help Ted Bundy into his car would probably have run away screaming from him instead....
Be that as it may, in meting out capital punishment to anyone, be it Ted Bundy or some drug addict turned robber and murderer, or any other person - society dehumanizes itself. That's the long and short of it, to me. It renounces basic human rights. That's the last tragic impact of people such as the above mentioned - that their heinous crimes make it easier for society and legal systems to turn to "an eye for an eye" as justice, turn to a system of revenge and retribution and consider it justified; - thereby losing some of our precious shared humanity in the process.... in addition to also making killers of the ones who are to administer the punishment.
I don't see why those in favour of the death penalty are so dead set on its continuation. What harm to society is there in keeping even sadistical serial killers firmly behind lock and key - treating them humanely but certainly never letting them out into society again? When the very fact that they, even *they*, are treated humanly in prison serves to remind us all that society as a whole will and should demonstrably *not* sink towards their level in *any* way, shape or form: What they did in taking lives (not to mention the how and why and how often of it) was unconscionable and outside the realm of acceptable human behaviour, and the punishment in pointed contrast should be humane, though certainly not naive. "An eye for an eye makes the world blind".