he knew it happened
A historically false claim, it is not necessarily Iran, but their leaders who deny the Holocaust. They do this a part of a series of other absurd claims in order to justify destroying Israel.
Many Muslim countries do not recognize Israel.Some Arabs and some other Muslims believe that the Holocaust is misused to enhance the legitimacy of Israel.Many go a stage further and find it convenient to deny the Holocaust altogether.
When 5-star general Dwight D. Eisenhower witnessed the liberation of Ohrdruf concentration camp, he knew people would deny it and he wanted the entire camp filmed. Today, there are some people who deny the Holocaust; all of them are anti-Semitic and hate Jews for one reason or another.
Of course it's not illegal in the US. There are 15 or 16 countries in Europe where it is illegal to deny the Holocaust in public.
Please have a look at the related question below, which may answer your question.
"The American Historical Association Council strongly deplores the publicly reported attempts to deny the fact of the Holocaust. No serious historian questions that the Holocaust took place." See link for reference and for background.
Yes it is, as well as 12 other countries. (Note that this relates to public denial).
Many Catholics were killed during the Holocaust, particularly Slavs, Poles, 80% of the Catholic Clergy of German were sent to concentration camps in 1939. 2,600 Catholic priests from 24 different countries were killed.
Those who deny the Holocaust often have various motivations, including anti-Semitic beliefs or ideologies, attempts to spread misinformation or propaganda to promote their own agenda, or denial of historical events to protect their own national or ideological identity. Additionally, some individuals may deny the Holocaust due to a desire to minimize or downplay war crimes and atrocities committed by their own country or group during World War II.
By remembering those who were lost and facing up to those who deny the existence of such an historical event. Never Again.
The term "holohoax" is used by Holocaust deniers to promote the false idea that the Holocaust is a myth or exaggeration. It is not attributed to a specific individual but is part of a broader lexicon used by individuals and groups that deny or distort the historical facts of the Holocaust. This term is considered deeply offensive and is associated with antisemitism and the denial of a well-documented historical atrocity.