There is a moment in the still heavily redacted CIA inspector general's report into its use of harsh interrogation techniques against al-Qaida suspects that speaks volumes of how torture is allowed to become acceptable.

Oddly it is not to be found in the details of the most egregious abuses: the mock executions, the simulated drownings and physical abuse, the intimidation with power drills or guns or the threat that one's family may be killed or raped. Instead it is to be found in a discussion between a CIA interrogator and the agency's headquarters about a technique an officer had found to be effective.

The discussion, from 2003, centred on the use of "water dousing" – which involved placing the detainee on a plastic sheet and flooding him with water for 15 minutes.

The reply is fascinating in a chilling way. In its advice, attempting to mitigate the risk of any future prosecution, it suggests the detainee should not be placed naked on a concrete floor but on a towel or sheet. The air temperature, the cable from heaquarters continues, must exceed 18 degrees centigrade if the victim is not to be dried immediately. In these words there is the awful intimacy that violence requires.

It would be easy to see in such an exchange a concern for the rights of the prisoner. What it reveals in reality – as do the torture memos constructed by the likes of John Yoo and Jay Bybee that supplied the legal framework for the CIA's "enhanced interrogation" techniques – is something of the intellectual processes and conversations behind the rationalisation of torture in the George Bush era.

In his book Obedience to Authority: An Experimental View, Yale University psychologist Stanley Milgram described the experiment he had devised about the willingness of persuading participants to obey authority figures in inflicting what they believed to be extreme and dangerous pain on another human (65%). The work of Milgram and Leonard Bickman after him demonstrated the general innate tendency of people to obey figures or institutions of authority even when it was not in their best interests – a situation intensified in institutions, like police, the military and security services, whose membership both tends to be more social conservative and in whom the values of discipline and obedience is deliberately fostered.

But this is not a question simply of authority. What is demonstrated here is that other processes are at work as well. And while both Republicans and Democrats, including Barack Obama and again on Monday former vice-president Dick Cheney, have tried to insist that individuals officers should not have to bear the burden of guilt for a wider policy, what is clear – as US attorney general Eric Holder has recognised – is that even within the context of obedience to tasks set within the context of a national security interest, the defence of only obeying orders is never a valid one.

What is critical about the quoted exchange is the way that it has joined up the dots. It demonstrates that at every point in the chain of command and conception of the policy, individuals were actively investing in it both intellectually and morally.

For while we have long known, through the release of the torture memos, about the legal framing and design of a torture policy that came down from above, what has been absent has been the raw detail of the keen individual torturer's own rationale.

Now we can see it. How the men set to the task of torturing – released largely from normal constraints – improvised wildly as they constructed their sordid scenarios. And we can see too what happened to individuals. How with the legal constraints on what they could commit so nuanced, so flabbily defined, again and again they would step beyond even what the authors of the programme had deemed to be acceptable.

It is this that the CIA and its political supporters have so long tried to suppress, the ugly reality of what was intended in the policy of "enhanced interrogation": what it does not just to the victims, but to the victimiser and the victimiser's organisation. Even to the state apparatuses that condone and encourage it.

What it demonstrates is how a permissive culture of violence always breeds abuses, especially when those committing the abuse have been equipped with a self-legitimising narrative.

There is one thing more. The need to supply a proper name to this. For while the use of all violence in service of the state inevitably requires special pleading, there is something in the cold conversation between men about the limits to the pain and suffering that they can inflict that speaks of nothing but depravity.

Peter Beaumont is foreign affairs editor at the Observer. He has reported extensively from conflict zones including Africa, the Balkans and the Middle East, and has written widely on human rights issues and the impact of conflict on civilians. The winner of the George Orwell Prize for his reports from Iraq he is the author of The Secret Life of War: Journeys Through Modern Conflict

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