Ultimately what this means in practice is not only should you assume nazis are lying to you, because they're nazis, but you should also realize that in the rare moment a nazi is actually telling you the truth about something, this is only because doing so serves a larger purpose of manipulating you.
Again, they're people, you're not. They have agency, you are "an NPC." Never ever assume they see you as anything else, or you'll get the wrong answer.