Denying the Holocaust. Really?

How can you deny the fact that the Holocaust was a real and terrible event that happened in history when there is sources upon sources of information that proved it happened? There are a number of survivors that lived through this horrific event that can assure you that it happened. There are an endless amount of historical books that describe the devastating things that happened in the concentration camps. There are camps and gas chambers still standing today holding the memories of the human lives lost  in those places, hard proof that what the Germans did to these people were very much real. How can someone say it never happened? The fact that people can and would believe this scares me for the future. If we try to cover-up something like this it will happen again. We need to acknowledge our mistakes as a human race and to learn from them, not make up lies and conspiracies trying to cover them up. There is a colossal number of sources and proof that shows that this event happened in history and that it should never be forgotten, there is no reason for someone to believe the Holocaust never happened if you just did your research.