This is the core of the problem. The core argument I see being made -- not even mentioned in your list -- is the effective impossibility that the death penalty

This is the core of the problem. The core argument I see being made -- not even mentioned in your list -- is the effective impossibility that the death penalty can ever be fairly enforced in our justice system (given that it doesn't just err occasionally; it errs frequently and systematically). Combined, of course, with the uniquely irreversible nature of the death penalty itself. All the other arguments don't matter. Others disagree. If justice requires a life for a life, An assumption which not only everyone shares, but which is on its face quite problematic.