You can argue for or against the death penalty all you want, but the issue still comes down to acceptable forms of murder. If we murder someone for murdering someone else, we as a society are sanctioning the murder of the murderer. Alternatively, if we kill someone for doing something other than murder, we are sanctioning this form of murder as well. In either case, we are saying that it is okay to kill someone under those circumstances.
Go ahead. Claim it is “the state” doing the murdering, like the state is some giant amorphous blob. It’s not. There is a human on the other end of the button or the needle or the trigger or whatever form of weapon is used to end the person’s life. Sometimes there is a group of people, just like a corporation. The state is comparable to the court system, in some regard. Doesn’t matter. Still comes down to an acceptable form of murder.
I’m not arguing for or against here. I’m just pointing out that if you are for the death penalty, you sanction murder. It is as simple as that.