To many, its related to conspiracy theories and what not, so they dont believe it happened and believed the Jews staged this all so they can stand as head masters of the world, and to others, Hitler brutally murdered all the Jews he could find because he hated them for no justifiable reason, and there were evidence to prove this, so they believe it happened.
Trust me, there is a big number of people who believe and dont believe in it, so I dont think conspiracy theorists are people you should try and negotiate with since they firmly believe in what they read or hear.
But, same goes for those who believe its true, as to what if there is a conspiracy to make the Jews rule over all of us.
I dont stand by any side, an enemy of humanity is an enemy to all of us, but what we thought have happened and what happened in real life isnt necessarily documented in full truth.