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Those who advocate for torture based on hypotheticals are imagining themselves in situations where they would be extremely desperate, helpless and/or angry. They ignore any argument based on the ineffectiveness of torture, because they persist in imagining themselves in a situation where they would feel an overwhelming compulsion to do something.
What such people are trying to do, in presenting their hypothetical scenarios, is to conjure up a situation that will induce, in those with whom they are arguing, the same feelings of anger or helplessness.
As such, I believe that, if they examined their own feelings more closely, they would realize that the hypotheticals they describe are ones in which the impetus to torture derives, not from a need for information (or to accomplish a greater goal), but from feelings of desperation and helplessness.
Imagining a situation in which you would torture does nothing to rebut the arguments made against torture on grounds of morality, legality or efficacy, because you are imagining a situation where none of those constraints are relevant. You are explicitly imagining yourself unbound by such considerations.
You might as well be repeating, over and over again, "but what if you had to torture someone..."