It seems the term is being used in two ways. One is to highlight the historical connections between the Muslim world and Nazism and Fascism. For example, the founder of the Muslim Brotherhood was an admirer of Hitler and Mussolini. For another example, the Grand Mufti of Jerusalem met frequently with the Nazis to encourage them in the elimination of the Jews of Europe, and during the war he actually organized some Bosnian Muslim units to fight with the SS.
But the term is also being used in a generic sense, to say that Islamic sharia law constitutes a form of fascism, a form of totalitarian control of society.
The first use is factual and probably unexceptionable. The second is problematic, and forces the uniqueness of Islamic fundamentalism into the familiar mold of European fascism and national socialism.
But in any event, people who use the term should make clear what they mean. Eventually its spelling should be regularized too.