The unreliability of torture - and its often quite misleading consequence, with further damage to individual citizens - is a practical condemnation of the practice. That is not the main argument, however.
Respect for other people, respect for rights that unfortunately in today's world are too often abused or set aside, is the hallmark of a decent society. There is a golden rule: 'what you do not wish to be done to yourself, do not do to others'.
The moral argument against torture is overwhelming. The fact that today's bans and prohibitions are too much honoured in the breach is not an argument to legalise any aspect or purpose of torture. It is an argument to apply the ban more fiercely, to let the outrage of ordinary people condemn those that practise it or preach it.
I've tried to stay out of the bloginade on torture, because I thought that others were saying all that I had to say. Then along comes Malcolm Fraser, who was not my favourite prime minister when he was in office, and captures it precisely.
The issue of torture is not complex, intellectual or difficult. Torture is just wrong. Torture has no purpose except as a tactic of impunity to try and terrify the Other into submission. Torture degrades those who execute it and those who command it. Strangely, those who command torture always deny giving the command and that alone is enough to tell us the whole moral quality of torture. Torture is just wrong and we should all say that as often as we have to.