Mr Mussolini was a member of the Communist Party in Italy before creating its own version.
The main difference between socialism and fascism(also called national socialism) is that instead of accepting the International Socialist agreement(that was supported[paid by] and controlled by Russia by the way), they decided to be on their own, that is nation interest are a priority over international agreements.
The other important difference is that fascist were completely defeated, while communist won the WWII. That has made "fascist" an insult while "communist" is not.
You can make films about Hitler or Mussolini being terrible, but you can not about Mao big leap and cultural revolution for example. Most documentation on Russia's atrocities has been destroyed.