What is it with Muslims denying that the Holocaust ever happened? I had to unfriend on Facebook, a guy who was a Sharia Law promoter and Holocaust denier. I just can't tolerate that type of ignorance.
That has less to do with Muslim than with Arab. Nationalist Arab leaders pretty successfully managed to rile up their populations against the Jewish immigration to Palestine since the early 1900s by adopting common European anti-Semitic stereotypes, and when the new state of Israel was created after WW II, many Arabs were easily convinced that the Holocaust was a fiction invented by Jews and their minions to justify their takeover of previously Arab lands. The fact that a number of former high-ranking Nazis escaped to Arab countries and ended up "advising" their governments probably contributed, too. And somehow, these beliefs have stuck and probably will as long as the Arabs will oppose Israel's existence.
As for the question why the Nazis murdered the Jews, that topics is a bit too big to cover in a forum post.
To touch on the main points in one sentence,
- the conflict started 2000 years ago when Christianity split from Judaism,
- continued with about 1700 years of religiously motivated discrimination and sometimes persecution of the Jews of Europe, sometimes worse, sometimes less so, as they were the only major non-Christian group,
- got somewhat better in the 18th/19th century with the Enlightenment, which de-emphasized religion,
- then got worse again as new racial theories based on misunderstood genetics were applied to people in the late 1800s,
- provided "the Jews" as evil scapegoats for all occasions, even totally contradictory, both as immoral banker-capitalists (like the Rothchilds) and dangerous revolutionaries (like Marx),
- and finally ended up with Hitler, whose beliefs weren't that untypical for Europeans (or for that matter, Americans) of the time, but who unfortunately, due to specific political circumstances in Germany mostly due to the loss of WW I, was put in a position to act on his beliefs.