Lots of people who who deny the holocaust are racists but not every one who has problems with orthodox holocaust narrative is racist, interestingly a lot of Historical revisionists or Holocaust deniers (depending on your prejudice)have come to their views on this issue through the study of the conventional presentation of these terrible events and not through reading racist hate sites.
The big problem with the accepted Holocaust story is that there are two competing narratives of this event or events, one is that there was an official policy by the Nazi government to exterminate an entire ethno/religious group to support this view there are numerous witness testimonies but very little in the way of hard evidence i.e. forensic autopsy reports ,documentry evidence is scarce apart from some paperwork which is open to intepretation.
The other narrative is that the disasters which occured in the camps Germany and Eastern Europe were caused by the vissicitudes of war rather than by a deliberate policy of extermination by the Germans.
The evidence for this view comes from organisations like Red Cross and the Allied forces who liberated the camps their official view was that most of the victims who died in these camps died from disease , malnutrition, and ill treatment.
Another Reason for the demonisation of the Nazis could be the role of allies in creating the condititions which lead these horrific disasters .
the strategic bombing campaign which flattened Germany in the latter years of the war has been cited by the red cross as contributing to high mortality rate in the camps, with the breakdown of civil society these things just happen,