Ignorant statement. There are lots of sub-tendencies in communism, and they argue bitterly over their differences. Groups like tankies and Maoists tend to be authoritarian and pro-Stalinist, while Trotskyists hate Stalinists (guess why!), orthodox MLers dislike both for different reasons, many orthodox Marxists are skeptical of Bolsheviks, and then there are all kinds of socialist tendencies that don't identify as communists at all.