When talking to leftists, I find that they are more open to the linear government-control sliding scale model when I tell them that the medieval Roman Catholic church would be placed toward the left side of the scale (but not as far left as communists or Nazis). Since they hate Christianity, the leftists then seem more open to considering this scale.
Fascism is an authoritarian system and authoritarian governments have traditionally been leftist. The difference between fascism and communism is semantics. If they’re hauling you out and shooting you tied to a post for speaking against the government then they’re authoritarian and therefore leftist.