Ethics -The Nazi Euthanasia (T4) Programme - German citizens were gassed by the Nazis before 1939 - foreshadowing the mass murder in the concentration camps

                                                The Nazis held a warped version of Darwin's idea of the 'survival of the fittest' in nature and used this to justify killing fellow Germans who were mentally ill or depressed. Why then do the Holocaust deniers find it so difficult to accept that that the Nazis would most certainly have been capable of killing millions of Jews, Poles and Russians, gypsies and others?
http://en.wikipedia.org/wiki/Hadamar_Euthanasia_Centre