Yet, after thinking about this a bit more, I felt the urge to call your attention to Roger Olsen's response to the piece in order to show that Mohler does not represent all evangelicals on this matter. (Although I think he might represent a good number of evangelical laypersons). Olsen is an evangelical theologian who teaches at Baylor University.
Here is taste of Olsen's post from his Patheos blog:
I find Mohler’s defenses of capital punishment weak at best. The Old Testament “clearly calls for” many things—including capital punishment for a broad range of offenses including adolescent rebellion against parents. Certainly for idolatry. Does Mohler think we, as a whole society, should then expand the death penalty for all the offenses for which it is called for in the Old Testament? I doubt it. That makes his appeal to the Old Testament extremely weak.
Mohler seems to believe that IF the Bible calls for something American government should practice it. That’s a huge leap off the pages of the Old Testament to modern, secular government. He speaks disparagingly of secular government. Does he want a return to theocracy? If not, he should explain how his argument is consistent with a rejection of “Christian Reconstructionist” theocracy...
Advocates of capital punishment like to say that no innocent person has been executed. Since when? Nobody doubts that in the past many innocent people were executed. I suppose they mean in the recent past. But just recently serious doubts about one executed man’s guilt has been raised by experts including a special Texas panel led by a governor-appointed chairman. (The governor fired one chairman apparently because he was favoring the findings of the panel that Todd Willingham was not guilty of the crime for which he was executed.) Enough evidence of his innocence has been brought forward to now declare that he was almost certainly not guilty of the crime for which he was executed. The new governor-appointed chair and the governor seem to have stopped the panel from declaring Willingham to have been innocent....
Should Christians support the death penalty? Mohler asks. His answer: “I believe that Christians should hope, pray and strive for a society in which the death penalty, rightly and rarely applied, would make moral sense.” Why rarely? If murder deserves execution and murder is common, why should execution be “rarely applied?”
The fact is that capital punishment is never necessary which is the main reason ethical people, including Christians, should oppose it. Deadly force should never be used when it is not necessary. Capital punishment is absolutely never necessary. A stronger case could be made that sometimes torture, even of innocent persons who might have needed information, is necessary. And yet no Christian ethicists I know of supports torture. Now that the federal government and all states (so far as I know) have sentences of life in prison without the possibility of parole and solitary confinement for violent inmates (and if the they don’t yet, they can and should), capital punishment is simply not necessary for any reason—unless blood lust and vengeance is considered a valid reason for it.
If I could ask Mohler one question it would be this: How do you respond to the possibility that God might have some use for the life of a person the state executes? How is the state, supported by you and other conservative Christians, not cutting off God’s ability to use a person in the future?
There is also another dimension of this entire debate that needs to be addressed. Olsen's blog is read largely by fellow Christians who most likely share the author's belief in the authority of the Bible. Mohler, on the other hand, chose to publish his argument, which is based entirely on the presupposition that the Bible (in this case, Gen. 9:6) is authoritative and should be obeyed on matters such as capital punishment, at CNN. I don't know how many readers of the CNN religion blog accept this presupposition, but I am guessing that a lot of them do not.
So here is a message to my fellow Christians. If you want to enter the public square to make an argument about the rightness or the wrongness of a particular social practice, building your argument on a belief in the inspiration or the authority of the Bible is not the way to do it. Such an approach does little to persuade those who do not share your presuppositions.