Stalinism only seems different because it’s named after the dude, maybe fascism is a more generic term. All the person your responding to is saying is that it’s as natural an argument to say that communism leads naturally to fascism (honestly in a really similar argument to yours by saying the state isn’t distinct from the ruling class and that power naturally condenses to the top in the system.)
I could make a million arguments getting into the nuance of it, as I’m sure you could too. That’s just what the person is saying.
Never again will we miss getting on the ground floor of growing fascism