The analogy is not flawed because the comments you made are precisely my point: it's not a general, fundamental, moral conundrum -- it's that the death penalty is its own special beast. Graderjs argues from a general perspective using the example, but not limiting his arguments to, the death penalty. And then, as you and I point out, it simply does not hold up. It's the severity that makes it stand out, not the overall act of 'are we moral if we do the same thing'.

Graderjs also makes no argument about other justifications of 'punishment', and, again, I'm with you. Note that I often write 'punishment' in quotation marks. I don't believe (and the numbers between countries support that) that revenge is a productive reaction from a society.