Maybe torture is "constitutional in a ticking time bomb scenario" (NYT paraphrasing Justice Scalia), if there is a reasonable belief that that is the most effective means of thwarting a genuine crisis that is truly imminent and of that magnitude, although the efficacy of torture is in itself questionable. But that scenario is also very fact specific. The danger is that the powers that be will simply hide behind an illusory version of this scenario when it does not apply. This tends to make the state itself look like something of a terrorist entity, and thereby also tends, as we have seen, to actually reinforce the anti-state arguments of the violent resistance, helping them to recruit. I read our Constitution as cleverly designed to avoid all of these things. Proper due process allows the guilty to be convicted and removed from society, while also largely convincing the skeptical that the state itself has not run amok. So we should be very careful about allowing for suspensions of due process, and not allow the executive to paint more-scary-than-real scenarios in order to clothe what is really the naked will to power.
Follow up post:
If Scalia's argument, per MR's comment, is that cruel and unusual doesn't apply -- we might reply to Scalia that torture IS punishment. It's almost by definition punishment for alleged non-cooperation, presumably used in an attempt to force cooperation. Often, it's also an attempt by interrogators to punish the prisoner for crimes he is assumed to have committed. In either case it is meted out without Constitutional due process of law, and if it is "cruel and unusual" (which is hard to get around if it's really torture) it is almost certainly unconstitutional on that ground as well. So I back off the part of my previous post that agrees that at least in some farfetched scenario, torture might really be constitutional. Even if the world was about to blow up, torture would still be unconstitutional on grounds of cruel and unusual punishment AND lack of due process -- whether or not those are Scalia's arguments. However, at that extreme, one might still forgive torture, unconstitutional though it may be, at least in the also unlikely event that it actually worked. In a way this sounded to me like what Scalia must have meant -- in the worst case scenario, the ban on torture would seem absurd, and the Constitution couldn't be absurd. But to the extent that there are better alternatives than torture, such a ban is not absurd. It's also possible that the framers, being human, didn't think of every possibility, and there may be, if only once in a lifetime, a time when something unconstitutional is the only right thing to do. But Bush and Co. are only pretending that that moment has arrived, because they don't want anyone telling them what to do.
Of course, the "unusual" in "cruel and unusual" is a most unfortunate loophole, inasmuch as it seems to allow any sort of "cruel punishment", if only it is also "usual". I would think this was either a linguistic lapse or a compromise on the part of the framers (who after all, were human). Then again, it might eventually force the phasing out of cruel punishments -- if for example the death penalty was found to be merely cruel (how could it not be cruel to be told you will be killed?) and several jurisdictions banned it, while others used it more and more rarely, it would also become "unusual". Meanwhile any cruel punishments that were new or simply unusual would immediately be unconstitutional before they could have a chance to become "usual", so they could never cross over that threshold.
