Disagree. First and foremost, the death penalty is -- first and foremost -- the most appropriate possible punishment that society can impose. It's a matter of symmetry: If one takes a life, one's life is then forfeit.
If this also serves a deterrent purpose, then well and good.
If this also serves a deterrent purpose, then well and good.
The deterrent is "if one takes a life, one's life is then forfeit".
You say toe-may-toe, I say toe-mah-toe.