During the Russian Revolution, the Communists spent as much effort fighting other Socialists as they did the Czarist forces. In Cube, Fidel's revolutionaries persecuted other Leftists and Anarchists, even the Cuban Communist Party.

A Revolutionary Party must have total obedience and complete discipline. It cannot afford their ideological comrades to question their methods or goals because:

1) They cannot be easily dismissed as reactionaries or counter-revolutionaries.

2) They can gain support and followers from fellow revolutionaries who don't follow the Party Line.

The ENEMY can be dealt with, bargained with, compromised with if necessary. But mavericks in your own party pose a direct threat to leadership of the Revolution. That is intolerable. It calls into question the legitimacy of the faction trying to monopolize the revolutionary movement itself.

If you're not familiar with the term, look up "Night of the Long Knives".

Now do you see why Fascists hate to be called Fascists"?