Can the head shaving and the shoes thing have more than one purpose, though? I'm sure it was part of the process of dehumanizing these people as well as for cleanliness reasons, but I'm not a historian.

To be clear, I am not a historian either, however I am interested in this type of thing. Typhoid is a terrible disease which is often a primary killer of refugee camps (currently an issue with refugees of Syria). When you pack all those people together into really shitty living conditions, Typhoid quickly becomes the primary concern.

There certainly was an aspect of dehumanizing to certain actions in concentration camps, such as the serial number tattoos. Not everything in concentration camps was dehumanizing though. The Nazis allowed and provided supplies for the schooling of children, sports, and other recreational activities of the inmates. Take that with a grain of salt however, as it could also be observed as a mere attempt to distract inmates from the death factory.

Zyklon B (the chemical used in the gassing) was manufactured and used in most if not all concentration camps for the disinfectant of clothing. Health conditions at the camps were absolutely horrible. The primary purpose for destroying clothes upon arrival at the camps and the shaving of hair was first and foremost for preventative health measures. Similar practices were done in the Soviet Gulags, which also held terrible health conditions. There may have been an additional benefit of dehumanization to it, however that was most likely just an after-thought.

About the shoes - At Auschwitz, the DC memorial, and at the camp I was to in Italy, the mass piling of shoes and hair was used as a strong emotional tool to give a visual relatable sense to the number of people whom died. Its a chilling experience to see a massive room filled with bland shoes, knowing that the people whom wore them died because of the Holocoust. The reason they had so many shoes was because they had to be rotated out (actually I'm not as clear on this part) to be disinfected with Zyklon B. Zyklon B is powerful stuff, so when it was used, many articles of clothing were disinfected at the same time. The camps had buildings specifically for this disinfecting process.

How low does ones estimate of holocaust deaths under the official tally have to be before it becomes denial?

What defines something as sexist? Its in the eyes of the beholder, but once someone says the word sexist, its everyones problem. In our lovely tone policing world, any discussion surrounding the representative statistics of the Holocost can be labeled as denial, regardless of how academic. This has been used to make it practically illegal to talk about the Holocost in a factual sense at all in several countries.

There certainly are people who distort logic in order to justify true denial of the holocaust. It is hard to find the intentions behind an opinion on the Holocost because it can quickly degrade to a shallow attempt to promote a conspiracy theory. This has caused it to become a serious issue in discussion even within academics. On the purely academic front, they like to use the term Holocaust Revisionism, to move away from the stigma of the term Holocaust Denial.