Sure, it's 20th and 21th century templates. But the man was free to preach for 10-12 years, and then went homicidal. For me that means that even by 7th century Arabian template he was a fascist.
I find the labeling of any far-right, authoritarian or reactionary person/movement as "fascist" as annoying as when right-wingers in America call anything they don't like (like Obama), socialist, Marxist, or communist.
The problem with using terms like that as epithets is that it obscures the actual meanings of the words. Fascism did not exist before the 20th century and was a specific reaction to the political, economic and social conditions of the 1920s and 30s. Fascism may be reactionary and totalitarian, and Mohammed may have been reactionary and totalitarian, but that does not make him a fascist.