Just because Communists fought Fascists (e.g. in Spain) at some point in history does not imply the ideologies are opposite. Kings have been fighting Kings all through history and no one argues that one King was Left and the other King was Right.
Communism and Fascism are both totalitarian Far Left ideologies. Far right in American is Ayn Rand and Tom Palmer, purist Libertarianism.
I know, this is repetitive but it seems to be a prevalent meme, propagated I suspect to keep leftist Jews from leaving the congregation.