While this is a legitimate question, it seems like you assume a few things about anarchists and their "societies". While it would be possible for one entire anarchist community to disagree with another entire anarchist community (a community of anarcho-syndicalists vs a community of anarcho-communists, perhaps), generally anarchist disagreements occur and are resolved at a more individual level. Even if two anarchist communities did disagree, it would be irrelevant in every aspect but the personal, because neither community would have any kind of authority over the other. In my mind, the most immediate option would be to drop the issue and accept the difference in opinion, while the other option would be to have some kind of community debate, either leading to mutual agreement or a return to the first option.