If you look at slavery, gender oppression and inter-dyanmics, or the colonization of the Americas by whites, you will find that these historical contexts have all been extremely distorted by the left to suit their narrative.
For example, with slavery, when I attended elementary and high school not very long ago (I'm 27 now) I was essentially taught that only one kind of slavery existed: Evil whites enslaving innocent, law abiding blacks. From doing my own research over the years I've learned this dialogue is profoundly distorted and only quarter-truth at best, for example, mainstream society often omits facts pertaining to slavery such as the fact that Arabs actually enslaved more Blacks than Whites did, or that Blacks actually sold themselves into slavery, or that Blacks had also enslaved themselves before the White man ever came into contact with them, or that there are also millions of examples of White slaves who were enslaved by other Whites or nonWhites. The government, media, and academia have twisted the historical context of slavery to only suit their agenda and to encourage white guilt, so they present slavery in such a way that it is only viewed as whites enslaving blacks, when the reality of slavery is very different than that. Even movies, TV shows, and the news, essentially all of society around us works to push this leftist narrative.
Similar with the Holocaust, I'm not saying it didn't happen, but what I am saying is that it is likely extremely distorted in its presentation just like slavery is. In terms of the quantitative extent of the Holocaust it is likely distorted, the numbers seem to lack credible evidence and historical confirmation. It is also distorted in terms of it being presented as an attack only on Jews. I agree 100% with what werewolf says which is that the Nazis did not have a systematic policy in place to only target Jews. Moreover, crimes on a similar scale against nonJews are often omitted, overlooked, or censored. For example, the hardships that Russians, Poles, or later Germans went through. Instead the government, media, and academia present WW2 as though the Nazis were targetting Jews and only the Jews were killed and suffered hardship. Just like slavery, the reality is far from that and at best this narrative is partially true. Also, anytime a government needs to impose censorship onto the research into a subject, that is an immediate red flag. If what they were saying about the Holocaust was true, why would they need to impose a censorship into its debate?
The censorship of debate into the account of the Holocaust is not too dissimilar from the de facto censorship concerning human biological differences, or studies which correlate race and intelligence. Many prominent scientists used to document racial differences, and many of these scientists were experts and leaders, but today very few publications will publish a study that says something deemend politically incorrect, regardless of whether it is true. Anytime this level of censorship is present, its because the truth is not what their agenda is pushing.