It should be allowed to questioned, like any events in history, but as an anti-Zionist and a trained historian I have to say that the gas chambers are a proven fact.
There are some questions about number of casualties. 6 million deaths is not set in stone, but it's proven that at least 5.1 million people identified by the Nazis or their own authorities in demographics as Jewish died in World War II.
We also know that the number is higher than 5.1 million, but because the information from Soviet Union - where Nazis would often just gather Jews up and kill them when they conquered a village or town, without bothering to make records of their victims - especially has large differences in estimates, an exact number can never be established.
The main problem that I see with the Nazi genocide of Jewish, Roma and other minorities is that the public gets their view of it from fiction - books, movies and TV - which tend to concentrate on aspects that often give a distorted view of what happened.
Instead of "industrialized genocide" it was especially in the Eastern Front "normal" genocide. Larger amount - at least 1.3 million - of Jewish victims were probably shot than died in gas chambers (at least 900 000).
People were burned, hanged and drowned and at least 1.5 million died of famine and disease in concentration camps, work camps and ghettos.
