A few brief examples, from the testimony of Josef Kramer, Kommandant of Birkenau:
Did you prefer to be a party to wholesale murder rather than to be arrested yourself? - I did not partake in this mass murder.
Do you think that anyone is entitled to give or to execute orders for the mass murder of innocent people? - Probably there must have been somebody who issued these orders. I myself never saw them and have nothing to do with it.
I put it to you that not only were you present at these selections, but you took an active, and very active, part in making the selections yourself? - That is not true. It is a lie.
You heard witnesses here in person, one after another, and affidavits of dozens of other people read, with regard to the beatings which went on at Auschwitz. Do you say that never happened? - Yes.
Let me suggest to you that you beat so many people that you cannot remember any particular one? - I can only say I have not beaten any prisoner.
Irma Grese denied all allegations of abuse as well:
There was a lot of beating of prisoners there, was there not? - I did not see it.
I suggest this to you: that when you went out with these working parties you made a habit of beating women and of kicking them, and you enjoyed it? - And I say that you are badly informed about me, and that it is a big lie.
Gertrud Diament in her deposition said that your favourite habit was to beat women until they fell to the ground and then kick them as hard as you could with your heavy boots? - That is a lie. Perhaps it is her habit to lie.
These people knew they were being selected to die, did they not? - I did not know and the people could not have known either. Nobody knew why these selections were made.
Are you seriously asking the Court to believe that? - Yes.
Is it not right that it was quite easy to tell a selection parade because only Jews had to parade for it? - We were never told anything about it.
Throughout the testimonies, these examples seem to be common answers from former SS guards. I noticed that according to a large number of guards, they were never themselves part of gas chamber selection, it was always either someone else giving the orders for murders or beating prisoners, or it never happened to begin with, and almost all accusations of abuse by former prisoners were considered lies or exaggerations. And on top of everything, the most surprising part of all is that they seem to have zero emotional response or general remorse over what they were part of.
Have these reactions been studied at all? If so, what was the reason behind such blatant denial of wrongdoing or abuse in the camps? Was the average guard actually that naive, or were there actually very few guards who were involved with murder or abuse in Auschwitz-Birkenau?
This is a tricky question to answer in part because the rationale behind these types of defenses is going to vary widely between each defendant, their charges, and the actual trial itself. Nonetheless, there is one important piece of the puzzle: the defendants were German. Or, perhaps more accurately, the defendants and their lawyers were individuals accustomed to German legal procedure and law.
Under Sections 211 and 212 of the 1871 German penal code for murder, there was a pretty clear division between Mord (murder) and Totschlag (manslaughter). These Sections remained in effect throughout the Third Reich and the legal criterion for both differed quite markedly from American legal definitions. Totschlag was a much more expansive legal category than American manslaughter and could cover crimes that would be considered second-degree murder in a US courtroom. Additionally, Mord charges also investigated issues of motive and intent trying to prove bloodlust or other base motives. German law also made distinctions between being an accomplice and a perpetrator that were often quite subjective. A famous 1940 murder trial illustrated how this distinction worked out in practice. In this case, the mother of a newborn illegitmate child had convinced her sister to drown her child for her. Despite the fact that the sister performed the act, the German court ruled that the mother was the perpetrator both because she instigated the act and because it was in her interests, not her sister's, to murder the child.
The distinction between Mord and Totschlag and other aspects of the German legal system were ones that was pretty important to the defense of a number of figures brought to trial for the Holocaust. While these types of defenses made very little traction in the NMTs and IMTs, they proved rather thorny when the FRG courts began to prosecute German perpetrators in the 1950s and 1960s. A number of legal commentators in the FRG often castigated the Allied-run tribunals for ex post facto law now found that the subjective nature of German investigation was difficult to apply to Holocaust trials where the individual defendants tried to claim they were accomplices, not perpetrators. The German prosecutions also found that an inquisitional process quite difficult because the process of mass murder left relatively few witnesses who could testify about the defendants' mental states. Treblinka, for example, had around only 70 survivors at wars' end. These vagaries of German law were partly responsible for the seemingly lax punishments meted out in the German courts. An example of this was the first Treblinka trial in 1964/65; of the eleven defendants, only three were convicted of Mord and received life sentences, the remaining six were convicted of accomplices to murder with sentences ranging from three to twelve years, and one defendant, Otto Horn, was acquitted. In the case of Horn, the fact that he was on corpse burial detail meant that there were no witnesses to him engaging in activities described as bloodlust and evidence of his grumbling against the killings allegedly showed his mental state. Considering the fact that these men in the trial were involved in the operation of Treblinka's gas chambers, such sentences are quite light.
So there was a method of sorts to the madness of many of the German defendants. While "playing dumb" or being dispassionate in their testimony looks quite odd given the enormity of the crime, it could be a legal gambit that paid dividends, and occasionally (and I would add unfortunately) this tactic led to lighter sentences for those guilty of genocide.
Further Reading
Michael J. Bazyler, Frank M. Tuerkheimer Forgotten Trials of the Holocaust
Michael Bryant, Eyewitness to Genocide: The Operation Reinhard Death Camp Trials, 1955-1966
Hilary Earl, The Nuremberg SS-Einsatzgruppen Trial, 1945-1958: Atrocity, Law, and History
Devin O. Pendas, The Frankfurt Auschwitz Trial, 1963–1965 Genocide, History, and the Limits of the Law
I don't have a good answer, and I don't think there is a good answer. But I do have two have two recommendations that might help you grapple with this aspect of the camps. A fair warning: these are not happy books.
The first is Primo Levi's The Drowned and the Saved. Levi "survived" Auschwitz, at least in a physical sense; upon his apparent suicide in 1987, Elie Wiesel said that Levi "died at Auschwitz forty years later." The Drowned and the Saved focuses on the experience of the camps, with an emphasis on the impossibility of morality for both the prisoners and the guards, and the blurring of the lines between the two. As a consequence, Levi spends a great deal of time discussing evil and self-justification.
The second is Gita Sereny's Into That Darkness, a biography of Franz Stangl based on interviews after his arrest. Stangl was commander of both Sobibór and Treblinka, and so personally responsible for the murder of over a million people. Stangl exhibits all the characteristic denials you describe, but Sereny is there to press him to answer, and to acknowledge his crimes. In the end, he does, and is found dead of heart failure the next day in his cell. Sereny's critics have found her much too sympathetic to Stangl, but I feel such objections very much miss the point.
Hope that helps.