Holocaust imagery
The imagery of the Holocaust is treated by Holocaust deniers as propaganda, designed to demonize certain people and present other people as martyrs. That is obviously absurd and offensive, so Shermer reminds the audience through undeniable historical evidence that, no, the Holocaust did occur and its imagery remains a haunting and painful truth of human history. The truth comes in historical documents proving the existence of the Nazi regime and the well-known imagery of the Holocaust, the various tortures of the Concentration Camps, and the systematic execution of more than six million Jews.
Paranoia
Shermer, Grobman, and Hertzberg are not just historians; they are students of the human condition. They also treat the existence of conspiracy theorists as part of history, but they treat the allegations of the deniers as basically paranoid. The imagery functions this way: The theorists are extremely paranoid people, so that their threat detection and their ability to notice patterns is increased. Then, for various reasons, these people come to believe that the "powers that be" are always shaping human history and the narrative of history. This has a shred of truth to it, the authors remind us. But then their theories go on to be blatantly anti-intellectual and contrived.
Racism
Although Shermer and company decide that Holocaust denial is essentially paranoid conspiracy theorizing, they do not fail to mention that racism is obviously another key aspect of this. They could be denying any world event, but these people gravitate to the Holocaust typically because they have fully formed opinions about the Jews. Sometimes, people believe that Jews rule the world through a secret society or something, and then sometimes those people go on to believe that the Holocaust was basically just globalizing propaganda. That is a horrific racism, because the Holocaust brought a tortured and untimely death to nearly six millions of Jews with intentions of ethnic cleansing. To deny the Holocaust is to begin that anti-semitic cycle again.
Historicity and science
Shermer predicates his ideas on the scientific and logical treatment of facts gathered throughout time. In other words, he treats history with scientific accuracy, so that when he comes across anti-historical or pseudo-historical opinions that are contrary to fact, he is much like a scientist in his ability to refute those theories. The same is true of co-authors Grobman and Hertzberg. The three of them employ various scientific strategies to prove unequivocally that the Holocaust did happen and that the Holocaust deniers are essentially anti-intellectual conspiracy theorists.
