There are many people, particularly politicians, who are against the death penalty but want to make exceptions for terrorists or mass murderers.
I believe that if you are against the death penalty, as I am, the time to defend it most vigorously - perhaps counterintuitively - is when it is toughest to do so. That is when values and democracies are challenged the most.
Perhaps at no time in recent memory was the death penalty more tempting than in the case of Zacarias Moussaoui.
Convicted of helping to enable the attacks of Sept. 11, and with ties to al Qaeda, there was a very real desire by many to see Moussaoui killed as an act of revenge.
But there are practical reasons to keep Moussaoui alive. First and foremost, he can be a resource for insight and information on al Qaeda. Even if he was only marginally involved with the terror organization, as his defense team argued, he still may have information on key contacts, or chatter he picked up.
He can help our intelligence agencies better map out the mind of a fanatic involved in what he believes is a jihad. If he was highly involved with al Qaeda, as he himself later claimed, then he is a key player who might provide information that could help destroy the terror network, especially in the United States.
Now, here's the hard part.
Even given all the practical reasons for keeping Moussaoui alive, many would still say that for his role in the killing of thousands of innocent people, the only justice would be his death.
But even if Moussaoui were the so-called 20th hijacker, and a major enabler of the Sept. 11 murders, the death penalty would still be wrong morally because the only reasons for his execution would be revenge and the belief that he was beyond redemption.
As a Catholic, I have been taught that seeking revenge against sinners is a paved road straight to hell. The belief that a life can be redeemed, while a part of my church's doctrine, is not exclusive to it.
Indeed, the great leaders of our time who were victims of the most heinous crimes believed that the hope for redemption lives within all of us. Gandhi, Martin Luther King, Pope John Paul II and Nelson Mandela are just a few.
One day, I expect to be a mother. If my child - or anyone in my family - were killed, my first thought would be that I should kill the perpetrator with my own hands to avenge my loved one.
But I would be rejecting all the moral lessons I've ever been taught about the value of human life. And that is the very reason we don't allow victims to determine the punishment of the criminal. Because we were all victims of the attacks of 9/11.
Virtually all civilized nations have adopted this principle of redemption in their law, especially in Europe, which experienced the institutionalized nihilism of Nazi Germany. Amnesty International reports that, worldwide, executions in 2005 fell by more than 1,500, as more and more nations decided to eliminate capital punishment.
Of course, the United States ought not do things just because Europe and the rest of the world does.
We ought to lead them. On issues of morals, human rights and human dignity, the United States should set the example. It is time for people to demand that the United States, a beacon of hope and freedom, reclaim its place as the world's leader in establishing real moral values in the way it operates. There would be no better way to set ourselves down that path than ending execution, and there could be no stronger launching pad down that path than with the life sentence given to Zacarias Moussaoui.
Flavia Colgan is an MSNBC commentator. (She'll be on with Tucker Carlson at 11 tonight. ) And look for her new blog, CitizenHunter.com .