From the essay The Value of Free Thought quoting from page 95 onward (perhaps written in 1944):
The theory of the Nazis, however, is definitely worse [than Soviet Marxism under Stalin]. Let us consider its salient points. There is a master race, the Germans, which i sdivinely ordained to rule the rest of mankind, not for their good, but for its own. Originally it was thought that races akin to the Germans shared some of their merits, but this turned out to be a mistake; in Norway, for instance, there are no genuine Nordics except Quisling and a handful of followers. Non-Aryans are specially wicked, and the most wicked of non-Aryans are the Jews. The Japanese, on the other hand, are so virtuous that they may count as honorary Aryans.
The Germans, alas, have been corrupted by Jewish influences, notably Christ and Marx. What they were before this unfortunate poison got into their blood may be seen in the pages of Tacitus. When it has been eliminated, they will again perceive that war is the noblest of human activities, and the opportunity of tyranny its most splendid reward. Other nations, strange to say, seem blind to the superiority of the Germans, but it was hoped that tanks and planes would prove efficient missionaries of the new creed. This hope, however, is now rapidly fading.
No such tissue of nonsense could have been believed by any population trained to examine evidence scientifically, and to base tis opinions on rational grounds. Self-esteem, personal, national, or human, is one of the great sources of irrational belief; in the case of the Nazis, the self-esteem is national. Education should be directed, in part, to teaching the young to think independently of their prejudices, especially their collective prejudices, which are politically the most harmful. But this is not done anywhere; every national government finds national self-esteem useful, every rich government finds admiration of the plutocracy useful, every obscurantists government finds credulity useful. Nowhere, therefore, except among the esoteric elite of a few universities, is anything done to promote an honest attempt to decide questions according to the evidence. And so credulous populations are left defenseless against the wiles of clever politicians, who lead them through inflated self-esteem to hatred, from hatred to war, from war to universal misery. The modern advances in the art of propaganda have been met with no corresponding advances in training to resist propaganda. And so the populations of the world, one by one as ‘civilization’ reaches them, go down into a dark pit of madness, where all that is worth preserving perishes in aimless slaughter.
The creed that I am preaching, if it can be called a creed, is a simple one: that, if you have an opinion about any matter, it should be based on ascertained facts, not upon hope or fear or prejudice.
From my small hardbound copy of Understanding History (1957).