“The death penalty is not intrinsically immoral like abortion, therefore the state has no business banning it!”
Prescinding from the fact that the “prolife” people most ardently in favor of the death penalty have absolutely no problem with grave intrinsic evil when Dick Cheney is defending the cold-blooded murder of innocents for the greater good, it must also be noted that nobody arguing for the abolition of the death penalty says it is an intrinsic evil.
It is not intrinsically evil for one person to sell heroin to another (the buyer *might* be going to use it for some licit reason like a chemistry experiment). But it is still such a massively imprudent thing for the state to allow that the state outlaws it anyway.
The cost/benefit ratio of the death penalty, fiscally, morally, and spiritually, is so massively against the death penalty that the obviously sensible thing to do is to ban it.