Argument: Defining Holocaust denial is too difficult to outlaw it
Barbara Kulaszka. "What is Holocaust Denial". Institute for Historical Review: "Often overlooked in this controversy is the crucial question: Just what constitutes "Holocaust denial"?
Should someone be considered a "Holocaust denier" because he does not believe – as Matas and many others insist – that six million Jews were killed during World War II? This figure was cited by the International Military Tribunal at Nuremberg in 1945-1946. It found that "the policy pursued [by the German government] resulted in the killing of six million Jews, of which four million were killed in the extermination institutions." 
Yet if that is so, then several of the most prominent Holocaust historians could be regarded as "deniers." Professor Raul Hilberg, author of the standard reference work, The Destruction of the European Jews, does not accept that six million Jews died. He puts the total of deaths (from all causes) at 5.1 million. Gerald Reitlinger, author of The Final Solution, likewise did not accept the six million figure. He estimated the figure of Jewish wartime dead might be as high as 4.6 million, but admitted that this was conjectural due to a lack of reliable information.
Is someone a "Holocaust denier" if he says that the Nazis did not make soap from the corpses of murdered Jews? After considering the evidence – including an actual bar of soap supplied by the Soviets – the Nuremberg Tribunal declared in its Judgment that "in some instances attempts were made to utilize the fat from the bodies of the victims in the commercial manufacture of soap." 
In 1990, though, Israel's official Yad Vashem Holocaust center “rewrote history" by admitting that the soap story was not true. "Historians have concluded that soap was not made from human fat. When so many people deny the Holocaust ever happened, why give them something to use against the truth?," said Yad Vashem official Shmuel Krakowski. 
Is someone a "Holocaust denier" if he does not accept that the January 1942 "Wannsee conference" of German bureaucrats was held to set or coordinate a program of systematic mass murder of Europe's Jews? If so, Israeli Holocaust historian Yehuda Bauer must be wrong – and a "Holocaust denier" – because he declared: "The public still repeats, time after time, the silly story that at Wannsee the extermination of the Jews was arrived at." In Bauer's opinion, Wannsee was a meeting but "hardly a conference" and "little of what was said there was executed in detail." 
Is someone a "Holocaust denier" if he says that there was no order by Hitler to exterminate Europe's Jews? There was a time when the answer would have been yes. Holocaust historian Raul Hilberg, for example, wrote in the 1961 edition of his study, The Destruction of the European Jews, that there were two Hitler orders for the destruction of Europe's Jews: the first given in the spring of 1941, and the second shortly thereafter. But Hilberg removed mention of any such order from the revised, three-volume edition of his book published in 1985.  As Holocaust historian Christopher Browning has noted: 
“In the new edition, all references in the text to a Hitler decision or Hitler order for the `Final Solution’ have been systematically excised. Buried at the bottom of a single footnote stands the solitary reference: `Chronology and circumstances point to a Hitler decision before the summer ended.’ In the new edition, decisions were not made and orders were not given.”
A lack of hard evidence for an extermination order by Hitler has contributed to a controversy that divides Holocaust historians into "intentionalists" and "functionalists." The former contend that there was a premeditated extermination policy ordered by Hitler, while the latter hold that Germany's wartime "final solution" Jewish policy evolved at lower levels in response to circumstances. But the crucial point here is this: notwithstanding the capture of literally tons of German documents after the war, no one can point to documentary evidence of a wartime extermination order, plan or program. This was admitted by Professor Hilberg during his testimony in the 1985 trial in Toronto of German-Canadian publisher Ernst Zündel.
[...] So just what constitutes "Holocaust denial"? Those who support criminal persecution of "Holocaust deniers" seem to be still living in the world of 1946 where the Allied officials of the Nuremberg Tribunal have just pronounced their verdict.
[...] Let this issue be settled as all great historical controversies are resolved: through free inquiry and open debate in our journals, newspapers and classrooms."