One has to give Alan Dershowitz credit for testicular fortitude, since I very much doubt his advocacy of torture warrants earned him many friends in academia. Furthermore, I found his framing of the argument for the effective legalization of torture to be somewhat novel; Dershowitz does not seek to defend torture on moral grounds, but rather argues that since its use is inevitable in certain cases, institutionalizing the practice will subject it to greater scrutiny and thereby limit the amount and severity of torture that would otherwise occur "under the radar". If you truly oppose torture, in this view, the best course of action is to bring it into the light of day, even if that means partially legitimizing it.
My astonishment at Dershowitz's sheer (if fairly well-reasoned) audacity diminished somewhat when I realized that the logical structure of his argument for legalized torture was much the same as the standard argument for legalized prostitution: in essence, "This is not going away, no matter how unpleasant it is, so we may as well make it legal in order to ensure transparency and prevent the worst abuses." Just as anti-prostitution laws have failed to eliminate the demand for commercial sex, anti-torture laws and treaties have failed to prevent governments from engaging in torture when they have found it advantageous. In Dershowitz's view, the sub rosa nature of torture leads to greater abuse, just as, in the view of proponents of legalized prostitution, the underground nature of the sex business aggravates its worst aspects (trafficking and abuse of women, spread of disease, etc.).
I would not favor Dershowitz's institutionalized torture for the same reason that I do not favor legalized prostitution: even if bringing the practice into official scrutiny would decrease its use (a contention of which I am dubious), there are some practices which are degrading and unworthy of a civilized society, and should not be condoned. No doubt in Dershowitz's view I thereby shut my eyes to the reality of torture, but I fully recognize that certain moral principles (such as an aversion to torture and the duty to defend the lives of innocents) may sometimes be mutually exclusive. I simply believe that leaving the resolution of such situations up to the consciences of the individuals involved is preferable to institutionalizing any recognition of a barbaric practice such as torture.
Nor do I share Dershowitz's fetish for transparency; if the Wikileaks imbroglio has shown anything, it's that unbounded scrutiny of government action does not do unbounded good. Government should be held accountable, but that accountability must be balanced against the need of the agents of the state to navigate moral dilemmas in the service of the national interest. I have little doubt that the exigencies of extreme cases will always lead the state to do whatever it deems necessary; better to operate with that understanding than to legally debase our traditional aversion to torture; it reamains as a check on those who are tempted to stretch the boundaries of "necessity".
Dershowitz refers to this view as "the way of hypocrites". So be it. There are worse things than hypocrisy, and it is preferable to sometimes fail to live up to our standards than to abandon them in the name of accountability.