Obviously nobody was actually equating Cuba with the Nazis. Nobody in this discussion believes that Castro is ordering the extermination of millions. Nobody in here believes that Castro wants a land war with Russia, wants to invade Poland, or has any particularly threatening military aspirations.
Nobody in this discussion even believes that Castro and Hitler are even as evil or morally bankrupt as each other, despite the obvious geographic, temporal, political, or military differences.
You of course know all of this.
The comparison that was actually made was drawing attention to perceived similarities between defenses that are mounted or have been mounted for Mussolini and Castro. (Namely, pointing out that despite all the other bad things that have been said about [subject], at least [subject] excels in one particular way. The person who made drew attention to this perceived similarity perceives a similarity because they believe the "particular way" that the subject excels is of little relative consequence in the grand scheme of all of [subject]'s actions).
I could just as easily compare my ex-boss to Mussolini: "Say what you want about [REDACTED], at least he came in to work on time." In this case my "defense" of my ex boss is actually an sarcastic quip that is meant to be critical. However obviously I am not balancing or equating an ex boss to a 20th century Fascist.
I can compare apples to oranges ("oranges are more acidic and juicier, and apples are crunchier, although both are quite tastey"), I can compare apples to Hitler ("More people have enjoyed apples, and Hitler was a better painter than any apple that I have ever seen, although both are biological organisms") and I can certainly compare any world leader to Hitler and any government to the Nazis.
What I am certainly not doing is equating them. Mussolini's Italy and Nazi Germany were similar in many respects, and dissimilar in many other respects.