Nazi theory indeed specifically denies that such a thing as 'the truth' exists. There is, for instance, no such thing as 'science'. There is only 'German science', 'Jewish science' etc. The implied objective of this line of thought is a nightmare world in which the Leader, or some ruling clique, controls not only the future but the past. If the Leader says of such and such an event, 'It never happened' - well, it never happened. If he says that two and two are five - well, two and two are five.