I'm a trusting person by nature, so it's useful for me to reflect on how deceptive people can be. The following excerpt really helped focus my attention. It's from a speech given to the Associated Press in 1933 by Adolf Hitler.
Speaking deliberately as a German National Socialist, I desire to declare in the name of the National Government, and of the whole movement of national regeneration, that we in this new Germany are filled with deep understanding for the same feelings and opinions and for the rightful claims to life of the other nations. The present generation of this new Germany which so far has only experienced the poverty, misery, and distress of its own people, has suffered too deeply from the madness of our time to be able to contemplate treating others in the same way. Our boundless love for and loyalty to our own national traditions makes us respect the national claims of others and makes us desire from the bottom of our hearts to live with them in peace and friendship.
(from Noakes and Pridham, Nazism, 1919-1945, vol.3)
Six years later, of course, Hitler notoriously told his military commanders:
I shall give a propagandist reason for starting the war, no matter whether it is plausible or not. The victor will not be asked afterwards whether he told the truth or not. When starting and waging war it is not right that matters, but victory.
Close your hearts to pity. Act brutally. Eighty million people must obtain what is their right. Their existence must be made secure. The stronger man is right. The greatest harshness.
The standard litigator's trick is to ask "Were you lying then or are you lying now?" Here's one case where we know the answer.