The prison guard is there by choice, just as a soldier is on the battlefield in Iraq by choice. He places himself in harm's way as a great sacrifice for the public. Although his life is worth as much as yours and mine, he accepts the risk, and so, the nobility of his calling. The public at-large has a reasonable expectation not to be a victim of violent crime, the prison guard knows his risk is greater.
Furthermore, as I've mentioned, executing murderers doesn't remove the danger of a prison guard being killed by a lesser criminal. The only way to completely protect prison guards is to either not have prison guards, or execute everyone.
If you and the law would support a regime wherein such mad dogs are strapped in restraints 24 hours a day and fed remotely via an IV so they do not have to interact with any other human beings ever, then I would agree that the claim of "necessity" would disappear in such cases. So would dignity as well, of course.
This will eventually be accomplished with robots, and without strapping people down and feeding them with an I.V. I wonder how many people will suddenly oppose the death penalty when that comes to pass. Not many, I'd wager. Even so, such conditions would not prevent the criminal from maintaining a relationship with his Creator, and its certainly not an inherent indignity to be isolated, when one considers the life of a hermit.
But some people, even outside of war and civil anarchy, need to go.
I'd hate the worthiness of my life to be a matter of opinion. Opinions change you know, and it's certainly not unheard of for governments to suddenly be of the opinion that Christians are worthy of being put to death. Our society rejects Christ, our courts don't believe in the sanctity of life, our doctors are gradually gaining the power to end life at their own discretion, and a nation just north of us has essentially categorized the Bible as hate speech. If we don't reject the death penalty here and now as an affront to human dignity, when the time comes, we're going to be the first ones lined up against the wall, I assure you.
Someone serving life without parole in a system where life without parole is the severest punishment has no fear of receiving a harsher sentence, so he is not incentivized to not kill guards and fellow inmates.
Someone serving 5-10 for robbery and aggravated assault is incentivized not to kill prison guards.
I'd hate the worthiness of my life to be a matter of opinion.
I am not referring to matters of opinion. I am referring to the fact that certain inmates will kill a guard if they have half a chance to do so.
Comparing murderers who try to kill guards to Christians imprisoned for their faith is more than a little silly.
We're moving into Mumia Abu Jamal sympathizer territory in which all prisoners, by virtue of being prisoners, are unjustly incarcerated prisoners of conscience.