Whoever told you that had an agenda.

First, communism is an economic theory. A very stripped down version of the theory is this: It proposes that the rich have obtained their wealth through the exploitation of workers. They justify the exploitation by “owning” the raw materials, tools, factories, land, and other apparatuses that the workers need to produce things. But without workers those things could not be converted or used to convert raw materials into goods. The theory suggests that the workers should own those things instead of the rich people. The idea is that the workers would then share amongst each other because, being of the same class, they are naturally more likely to care about the needs of the others in that class. Whatever your opinion or critique of this general idea, it is an idea not a cult.

Like all theories that have some level of popularity it has a lot of variations and sub theories. Some are more idealistic than others. These factions have a lot of history with one another a review of the Russian revolution and lead up show the kind of factionalism that exists with the movement. If you study revolutions you know that this is common.

Second, people have used virtually any ideal to justify atrocities. We should not throw out an idea only because someone somewhere used it to justify violence.

Third dogma is a problem. It is used in communist communities in the same way that it is used in the Catholic Church, to try and prevent descension. As noted above communist movements tend to have a lot of factions but the one that gains the most traction always tries to force the others into line. This is common wherever there are new ideas being implemented as policy.

This is likely why people think communism is intent on murdering its enemies. However, every revolution, Russian, French, Haitian, United States, etc. used violence and murder to achieve its goal.

Communists also say that capitalism murders people every day, and they die with a smile on their face. A pittance of a paycheck goes in their widow’s purse while they have died without realizing that they were exploited to death.