You seem to point out what is my biggest issue with self-proclaimed anarcho-communists; they seem oblivious to the dichotomous nature of their ideology.
Communism is obviously a collectivist ideology, and as soon as a collective is formed, an "out-group" -- consisting of those who reject the ideology of the collective -- is created as well. The mere existence of said out-group will obviously pose a threat to the collective, which, in turn, will attempt to oppress or subvert it.
In my opinion, this hegemonistic practice seems utterly incompatible with anarchism. Also, any form of collectivism usually ignores the agency of the individual and instead seeks to satisfy the perceived needs of the collective (and, as you mentioned, by whom should these needs be defined?).
I'll have to read up on the exact tenets of ANCOM, but it seems to me that every collectivist ideology will invariably end up oppressing individuals.
RE: So I encountered an Anarcho-Communist and this is my discussion/debate invitation...