Well, if you replace "fascists"/"Nazis" with "totalitarian threat" -- the former is modern shorthand for the latter but obviously want used that way until after experience of their rule established that perception -- a big part of the Nazi schtick was portraying other groups that way (Communists, the supposed global Jewish conspiracy, etc.)
Yep! The communists claimed the social democrats were fascists because they wanted to own the left, for example.
No, in particular since neither national socialism nor fascism was a boogeyman then.
Before the Nazis came to power, there were plenty of people in Germany who thought the Nazi party & Hitler were thugs and dangerous.
Yes, but they were not a boogeyman, like I said. Where you can just say "you are a nazi!" to shut down any discussion of anything you please. There's a difference between "some people didn't like them" and being a boogeyman.