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If Bush had waterboarded high-value AQ captures during the first week after 9/11 in an effort to discover whether other plots were imminent, then most Americans would have excused him, I believe. And rightly so.
But that gets to the futility of what you are trying to prove with the exercise - the importance of the actual reality, not just the abstract hypothetical. The government did in fact waterboard suspected members of AQ in the immediate aftermath of 9-11 (not sure if it was precisely a week after, but certainly soon after), and by nearly all accounts these practices not only did not yield useful intelligence, but in many cases produced bad information (in addition to ruining lives and causing all the other pernicious effects regarding terrorist recruitment, etc.).
Some weeks ago I noted the basic conundrum that the same exigency (ticking time bomb scenario) that someone like you thinks counsels in favor of torture in fact informs us of its lack of usefulness. That is, in an emergency situation where time is rapidly running out, a terrorist could easily provide misleading information that in fact thwarts government efforts to prevent disaster, without enough time to check the veracity of the information.
The dilemma is that sometimes you simply cannot extract meaningful information from a human subject in a short amount of time, using any method. Many people can't seem to come to grips with this, and insist that the only fault is in the physical restraint of the captors. This is an emotional response that I believe is based at least in part in a desire to see a "bad guy" suffer in some way for something that has or might occur.
Gotta go.