The classic work by John T. Flynn: As We Go Marching (1944). Full text in PDF, now in the study guide.
If fascism is the work of a handful of brutal and lawless men, we need have no fear of it here. We are never without leaders both able and corrupt. But they are not sufficiently numerous and powerful to make very much headway against the peculiar structure of our government. If the phenomenon is merely a manifestation of the paranoid mentality of the German people then certainly we are in no danger of infection unless we, too, are a little demented.
But alas, the most terrifying aspect of the whole fascist episode is the dark fact that most of its poisons are generated not by evil men or evil peoples, but by quite ordinary men in search of an answer to the baffling problems that beset every society. Nothing could have been further from the minds of most of them than the final brutish and obscene result. The gangster comes upon the stage only when the scene has been made ready for him by his blundering precursors.