Warning -- another long one. I wrote this in repsonse to a National Catholic Reporter article my Father-in-law sent asking whether the torturers aren't more of a threat to national security than the whistle-blower.
I think that the American ideal of America and the reality of America in the world are often, often purposefully, at odds. The ideal that this is a country devoted to freedom and the pursuit of dreams and excellence both here and abroad; that this is a country that acts as a benevolent hegemon to the other countries of the world without exacting a price for our benevolence; that we somehow uniquely represent the political, social, and economic apogee of human kind.
On the other hand, however, America is a country in a horrifyingly imperfect world, run by imperfect people with contradictory interests. On the surface, we value peace, prosperity, innovation, education, and diversity, but in practice, Americans elect leaders who are nationalistic, conservative (even the Democrats), unconcerned with poverty, and apt to play up ethnic, social, and religious differences for their own benefit. The American media and American educational system breed citizens with little or no concern for the world outside America, and thus create a hermetic seal around knowledge that even the Internet has been unable to break. I think that one could argue that the Internet has had a larger educational impact on the populations of less free nations than on the US, simply because our media and educational systems are so much more efficient at brainwashing citizens with ideas of inherent American superiority.
This reality of America provides and enabling environment for the atrocities to which you refer. As far as most Americans are concerned, the government can do what it needs to to "protect our way of life" (let's not even get into whether or not they ought to), as long as it doesn't a) interrupt daytime TV; b) contradict parochial pseudo-Christian values; or c) expect common citizens to get their hands dirty by participating in any way. This is the outcome of the media and educational system.
That leaves us with wealthy, well-educated, powerful men and women jockeying for position in a world of politicians and pundits. Of course, many of them are actually patriotic and honest, but even those have a warped view of their role as political leaders. There is no accountability mechanism in place to ensure that they actually help America reach toward the ideal. Who really cares about the ideal, apart from simply being able to hold it in one's head undisturbed? So, our political leaders take themselves and their need for power more and more seriously, and justify it with more and more conviction, using the ideal as cover.
But still, the question remains, how can men and women in the 21st century from a "civilized" country acquiesce to torture? I don't have an answer to that, other than that we aren't living in a civilized country. What civilized country in the world continues to impose the death penalty, even though it has been proven that innocents have been killed and that it might qualify as cruel and unusual punishment? What civilized country in the world consistently fails to come up with a serious plan for universal health coverage? What civilized country in the world blames poverty for the failure of education for the poor?
The torture doesn't surprise me at all, actually. We do not live in a civilized country. The only thing that we have left is a modicum of law and order in most places. Apart from that, the statistics on education, malnutrition, and health alone would make the US a prime candidate for development assistance.
So, is national security jeopardized more by those who torture than by those who shed light on it? Yes, definitely. But it is jeopardized most by those of us who can see the wrongs and don't get angry enough to act for change. Security is more than freedom from war. Peace is more than freedom from war. Peace is freedom from injustice. Those who at all turns threaten the justice of our society threaten national security in a way Saddam never could have.