I never got holocaust denial in total. Sure, you could go and argue it was in the low millions or something if you thought it was, but why would you argue it didn't happen at all? The people who seem to argue that most are the people who you'd have thought would be happy with the deaths of a few million juden.
The opinions vary a ton, some people saying it didn't happen or that the numbers were bullshit, the more intelligent ones will point out that the concentration camps were more or less the part with the lowest of "genocidal" deaths, as a fuckton of it was because of typhus and starvation.
One of the things people don't seem to realize is that Zyklon B was a delousing agent, used to get rid of lice and other parasites that are vectors of disease. That's why the "gas chambers" didn't exist, they were just rooms where people were shoved in and zyklon was poured into, to maximize the effectiveness per weight of product made, because they were more or less making it on-site.
The deaths to it is in the hundreds. Low or high hundreds we don't know. But basically all of those deaths were from people having acute allergic reaction to it, people being suffocated or crushed by the panic those groups often had by the fact they were packed like sardines in a tin, with the oil being zyklon and the only really breathable air being in their lung.
Then towards the end of the war, they started running out of food, and the already tight rationing became unsustainable, when the russians came to the concentration camps, they showed very little compassion to the jews either and their occupation included even less food than before that. If you go by the good ole addage "Communism = no food" then you can probably guess how many of them died of starvation under their custody.
It certainly didn't help that typhus was still a plague and that someone battling it requires more food than normal to provide to their immune system. it's no surprise that so many of the photos you can see have strong coloration on their back, a dead giveaway of a typhus death.
What should really be considered as a death from genocide would be the hundreds of thousands that died during displacement, where entire blocks were set ablaze, bombed, and the ones that still resisted the displacement being lined up in the countryside and shot into ditches, either made before the execution, or already part of the place.
That's why even netanyahu admitted some weeks back that hitler didn't want to exterminate them and wanted to send them down to the middle east:
"Hitler didn't want to exterminate the Jews at the time - he wanted to expel the Jews," the Israeli prime minister said.
"And Haj Amin al-Husseini went to Hitler and said: 'If you expel them, they'll all come here.'
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Disclaimer: I'm not really too well versed in all of it, but that's the more solid info i have on the whole situation. I might get shit wrong.