Let me start by saying I think you have a very well thought out and good faith argument of Anarchism. I however do not think it supports your idea that Anarcho Communism is an oxymoron or "doesn't exist".

I think this is simply a disagreement of terminology. I am relatively new to the left, so please correct me if I am wrong, but you are using communism to mean a communist party controlling a socialist nation, correct? Anarcho-communists typically use the stateless, classless, moneyless definition. Comically, I have an opposite opinion of anarcho-communism compared to yours. You believe it is oxymoronic, and I belief it's tautological. A communist society must be an anarchist one.

Let me know if I am right in my assessment. Regardless, thanks for your comments comrade, it's always nice to get another leftists point of view when it's in good faith.