"Fascism is a Lie" is the title of a short speech Ernest Hemingway gave to the American Writers Congress in 1937, reporting on his experience as a war correspondent during the Spanish Civil War. The speech is only one page in text, but manages to cover several different topics, from the profound to the prosaic.
Scholars of Hemingway, which I am not, have probably produced many dissertations on Hemingway's exact politics. Hemingway is not remembered as a doctrinaire leftist, and indeed, his machismo image might seem to be proto-fascist to some. But from the text of this speech, and how it accords with his service as a reporter during the Spanish Civil War, we can certainly see he is anti-fascist.
Although the speech covers many things, including the progress and methods of the war, it is probably most famous for its opening lines, where it discusses the relationship between art and politics:
For fascism is a lie told by bullies. A writer who will not lie cannot live or work under fascism. Because fascism is a lie, it is condemned to literary sterility.
Rather than attack fascism in terms of economics, in terms of it being a continuation of conservative politics, Hemingway believes that its most pertinent characteristics are its dishonest and sterility. Even the word "bully" is wonderfully descriptive: whether fascism benefits one economic class over another is irrelevant next to the fact that it is basically a system of government where the dumbest, meanest kids in middle school are in charge. And Hemingway's diagnosis of fascism as sterile has certainly been supported by history: except for a few brief fellow travelers (Martin Heidegger, Ezra Pound), fascism has never managed to produce anything that is meaningful artistically, in any medium. When it tries, it usually produces something kitschy and tacky, glaring and braying in its need to assert itself.
Fascism is a system that demands constant direction in the world. Fascism works on people's insecurities, promising them an omnipresent political and social world. Hemingway believes that the task of a writer is to find what is true, and to project it in such a way that it becomes the experience of the reader---and then adds that this is the most difficult thing to do. And that very difficulty is contrary to fascism. The idea that experience and meaning have to be struggled for and gained, and then that sharing them with others is supremely difficult, that a writer has to struggle over everything from high level concepts to the smallest examples of word choice---all of that is something that is incompatible at a deep level with fascism. But because they are scared of that uncertainty, fascists are stuck repeating the same clichés over and over, hoping that it can help beat down their fears, and they are stuck being unable to create anything meaningful.