They're both ideologically different and socially distinct groups, and for the middle of the 20th century were shooting at each other on that basis?
Both labels have become extremely overused. Not every authoritarian is necessarily Fascist, calling everyone a Nazi isn't useful, nor is calling relatively mild redistributive processes or universal healthcare Communist.
This was basically my point as well. There are certainly better words to describe concerns, and the concerns are more bipartisan than is popularly appreciated.
Both labels have become extremely overused. Not every authoritarian is necessarily Fascist, calling everyone a Nazi isn't useful, nor is calling relatively mild redistributive processes or universal healthcare Communist.