https://www.youtube.com/watch?v=3R9CZuCiNiA
Quite naturally one of the most elusive issues of all, that of knowledge, resurfaces again and again. Who knew what, and when - mainly in Germany? Over the last decade or so a spate of very detailed studies reversed Walter Lacqueur's hypothesis [...] that information was widely available but not understood. It appears now [...] that about 20-25 million Germans knew about the holocaust when it took place and clearly understood what it meant.
This exact question of knowledge has long been the basis of revisionist arguments, for instance Arthur Butz' formulation of the "invisible elephant" (see also this paper). The revisionist argument is that the alleged extermination camps had entirely inadequate provisions for secrecy, and widespread knowledge of the extermination would have filtered out, but that the actions of various governments and institutions (the allies, the Red Cross, the Catholic Church, the German opposition to Hitler, the Jews themselves) as well as the behaviour of the press are inconsistent with such widespread knowledge.
This admission of widespread German knowledge (20-25 million!) makes the revisionist argument on knowledge absolutely unanswerable. How do you keep a secret that 20-25 million people know about? Given the number of people in the German government working for the allies, it is absolutely impossible that the allies would not have known exactly what was going on if 20-25 million Germans knew. We have come to another reductio ad absurdum of holocaust orthodox historiography: believing in the holocaust requires believing in the possibility of a secret conspiracy to which 20-25 million people are party. Jewish groups like to reply to all accusations of collusive activity by refuting the strawman of a great centralized Jewish conspiracy known about by Jews. Yet there are fewer than 20-25 million Jews, so it is more plausible that there is a great conspiracy that all Jews know about than that the holocaust took place.
The revisionist argument certainly doesn't need to stop at examining the behavior of institutions. Consider the lack of any serious record of the holocaust contemporaneous with its occurrence. If 20-25 million Germans knew all about the holocaust, and one in a thousand of those Germans kept a diary, and 10% of those who kept a diary mentioned the extermination of the Jews, and 10% of those diaries survived, we would have 200-250 German diaries mentioning Jewish extermination! Or consider all the letters these 20-25 million Germans would have written. Or the impossibility of enforcing the use of a euphemistic coded language by 20-25 million people.