I do not overlook the fact that there are irrationalists who love mankind, and that not all forms of irrationalism engender criminality. But I hold that he who teaches that not reason but love should rule opens up the way for those who rule by hate. (Socrates, I believe, saw something of this when he suggested that mistrust or hatred of argument is related to mistrust or hatred of man).
Vol. 2, Ch. 24 "Oracular Philosophy and the Revolt against Reason" - The Open Society and Its Enemies (1945)