So the State, having decided that murder is illegal, resorts to murder as "punishment". That is hypocrisy of the highest order.
"I'll take 'arguments that can be used against prison and kidnapping as well' for 10 points."
THIS.
I'm actually NOT in favor of the death penalty. But I'm tired of stupid arguments surrounding this debate. You want to argue against the death penalty? Great -- I applaud you. But learn some basic logic skills.
Most of the times that the government has a law which requires a citizen to do something, it is likely doing something which would be illegal for private citizens to do. To wit:
- If police officers arrest people and detain them (for specific reasons), it is legal. If you do this as a private citizen, it is generally considered "kidnapping." As the parent says, same goes for prisons. Same thing goes for a court summons that requires citizens to show up (or be compelled by police to do so).
- If police officers are forced to restrain people physically (for specific reasons), it can be legal. If you do this as a private citizen outside of imminent threats to yourself, it is generally considered "assault."
- If the government requires you to give it money in exchange for not taking your property away, it is called "taxation." If you do this as a private citizen, you're probably guilty of "extortion" or perhaps some other form of "racketeering."
Etc.
Generally speaking, unless you're an anarchist, you accept that the government has powers to do things that would be "crimes" if private citizens would attempt them. The government is empowered to do these things to maintain order in society, to provide services for society, etc.
I'm sure people will disagree about the exact scope of these powers and governmental authority, but especially if we accept the notion of any "police power" in the state, we are acknowledging that the state will go around kidnapping ("arresting") people, extorting money from them ("fines"), or perhaps confining them for long periods against their will.
Should such possible state actions extend to killing people? Most people again tacitly allow such actions in the case of war -- as long as we are killing "the right people." Does the state's power extend to killing its own citizens? Well, until the past century or so, it was common to "summarily execute" (murder?) soldiers for things like desertion or aiding the enemy with relatively little due process. Nowadays we are having similar debates about "enemy combatants" and drone strikes which may target and/or inadventantly kill American citizens.
So, the death penalty is simply another place some people might want to draw the line. You may think the state should not have such a power. But it is ridiculously naive to argue that any action the state takes against criminals should be subject to the concept of "hypocrisy"... unless you're ready to accept that police should start having discussions like -- "Well, gee, this guy kidnapped someone and put her in handcuffs... so, well, it would be hypocritical for us to put him in handcuffs and force him to come to jail... so, well, I guess we just let him go! Can't be hypocritical, after all!"