But to me, that's a point in its favor. Let's have no illusions about what we're doing when the state carries out the killing of captive prisoners. I imagine support for the death penalty would decline rather quickly once heads started rolling.

That's not what Bunch intends. He explains why he favors the death penalty:

I believe the studies that show the death penalty does nothing to deter crime, yet support it anyway ... there are some crimes so heinous that there can be no forgiveness from society. This plays into my whole theory of the judicial system, which is that we should imprison fewer nonviolent offenders, rehabilitate those prisoners who can be rehabilitated, and severely punish the rest. I also think we should probably execute fewer people and heighten the standards of evidence required before an execution can be obtained, but that’s a post for another day.

But a prisoner can be kept alive without forgiving him for his crime. And locking a man away for decades with no hope of ever being released is arguably a more severe punishment than death. On its own, this case for the death penalty isn't enough.

One powerful case against the death penalty is its irreversibility.

Here's another argument against it: Even if there's a case where there's absolute certainty that the condemned is guilty, the execution still requires an executioner. Insofar as in individual takes on that role, he does damage to himself. (It's no accident that firing squads are organized so that no one knows who fired the fatal shot.) And insofar as the executioner acts on behalf of society generally, he undermines that most crucial moral norm, the inviolability or sanctity of life.

This punishment isn't worth the costs it imposes on us.

So let's bring back the guillotine—and once it forces us to confront the barbarity of needlessly killing people who pose no threat to us, let's abolish the death penalty. Countries without the death penalty get along just fine, and I don't think Americans will be able to stomach it once they look it squarely in the face.