Torture Erodes the Character of the Nation That Tortures
A nation is a collective moral entity with a character, an identity across time. Causes come and go, threats come and go, but the enduring question for any social entity is who “we” are as a people. This is true of a family, a church, a school, a civic club, or a town. It is certainly true of a nation.
Senator John McCain has said, “This isn’t about who they are. This is about who we are. These are the values that distinguish us from our enemies.” In a November 2005 Newsweek article, he put it this way: “What I…mourn is what we lose when…we allow, confuse, or encourage our soldiers to forget that best sense of ourselves, that which is our greatest strength—that we are different and better than our enemies, that we fight for an idea, not a tribe, not a land, not a king…but for an idea that all men are created equal and endowed by their Creator with inalienable rights.”
McCain is saying something very important here. His worry is that any move toward torture threatens our national character, our shared values, and our goodness as a nation. He rightly acknowledges that our Islamist terrorist enemies do not share our commitment to the rule of law, to human rights, to procedural justice, to limits on what can be done for the cause, however holy. This is tragic, even evil, and it makes them a particularly lethal and insidious threat, but it does not somehow settle the question of how we as a nation should respond.
We often say in church circles that people of integrity respond to life on the basis of scriptural principles, not preferences, feelings, or circumstances. We act on the basis of who we are, not who others are. If someone is ruthless to us at work this does not authorize biblical people to be equally ruthless in return. If someone violates their covenant with us it does not authorize us to do the same to them. Mature persons, and nations, know what their core values are and seek to act in every circumstance in a manner consistent with those values. If they abandon those values when severely tested, it raises real questions as to how deeply such values were ever held.

"Mature persons, and nations, know what their core values are and seek to act in every circumstance in a manner consistent with those values."
If there are membes of our society who do not share your value system regarding torture, then they are not subject to the problem underlying this argument. We now face a question of which person's values should dominate, an arguement far beyond the scope of this comment.
While you didn't structure it properly, you have here certainly the best of your arguments so far. It establishes that the choice by a subset of society to torture has real and negative consequences on members of the group who do not accept torture as acceptable. Economics calls this a negative externality.
Equally, however, the choice not to torture... and perhaps to allow an incident of terror to occur... has negative consequences (indeed, possible death) on members of society who do not agree with your moral code.
I submit that loss of life would, on any moral scale, exceed personal emotional harm from moral inconsistency. IF torture could save lives, therefore, I believe that people free of your "values" problem would have the stronger case.