A group of peasants or workers who own their farm or factory don't call themselves communists, and operate perfectly well within purely capitalist framework. They buy and sell what they want on the open market and use the same capitalist legal system.

Whereas people who call themselves communists, without exception, go to defend one of dozens bloodiest and nastiest regimes to ever exist. If an ideology brings sociopathic butchers to power not once not twice, but every single time, it's a good time to realize there is something deeply wrong with it.