Punishment.

My teacher in one of my classes said something very interesting today that made me think of the topic of punishment on pg 251. As he was explaining the reoccurring theme in movies, he came to the conclusion that in every movie, "Villains have to be punished." On hearing this this instantly reminded me of what I read in chapter 15 and how I felt about it. The book states, "we cannot help but hold people responsible for their actions: they ought to be praised and rewarded for their virtuous actions and blamed and punished for their vicious actions. We may call this the responsibility thesis." The book also gives examples of those who deserved to be punished,"racists who harm others......Adolf Hitler and his Nazi followers." I agree to the fullest with these statements. I do believe that the unjust/immoral acts of others should be punished and thy should do hard time for hurting/offending people. This is why we have time out and "spankings" for children and prison for adult offenders. The point that I am slowly driving to is; since it is OK for people who do crimes to do the time; morally is it right for humans to enforce the death penalty?
There are many states that use the death penalty, whether it be the lethal injection,electrocution, gas chamber, hanging, or even firing squad. Are we authorized as humans to kill another human? Why not let them stay in confinement for life instead of taking their life as their punishment? Why do they want to play God? I believe in punishment for crimes, but there is no justification for killing people at all!