Because that is a common thing for holocaust deniers. The majority of them is smart enough to not deny its very existence outright. Being more subtle, they decrease numbers, sometimes a lot, deny certain atrocities. Quite often they end with comparing these new, and totally false, numbers with Stalin's atrocities. All to come to the conclusion, that the holocaust wasn't even half as bad as everyone believes. Ah yeah, and that the Wehrmacht was totally not involved in this non-existent and despicable crime against humanity.