Mark Kleiman unwittingly expresses a case for limiting government in general:
This is a special case of an underappreciated general principle: the difficulty of judging consequences in advance means that we should pay more attention to means, relative to ends, than would appear at first blush. Since it’s easy to know that torture is horribly wrong in itself, and very hard to guess the circumstances in which it would prevent something even more horrible, a flat “no-torture” rule may well have better consequences (putting the moral absolutes aside) than some nuanced rule.
In that way, refusing to consider the use of torture is like respecting the results of legal processes or not cheating to win elections. It reflects not only a decent respect for the humanity of other humans but a sensible evaluation of one’s own ignorance.