Capitalism is a system in which individuals own and control property. Communism is by nature enforced by violence.
Discussion
The question is whether authority and dominion comes from within or from without. It's easy to tell where someone lands depending on how they feel about this dichotomy.
Preaching to the choir. I was just saying they might have different definitions in their mind (i.e. they say capitalism when they really mean crony/state "capitalism"). For instance, I'm sure you're for communes as long as they are voluntary. But I agree, if it requires aggressive force from a central authority (whether a dictator or group) ancom becomes an oxymoron.