According to some scholars and philosophers, ethnic identities are the best political, social, economic, ethic (and even aesthetic) alternative to State centralism, which is incapable of dealing with cultural diversity. Ethnic communitarism is then defined as a more authentic, humane, democratic and inclusive form of organization. The Welsh colonies of Chubut (Argentine) and the established Mennonite colonies of the Chaco Region (Paraguay) are two ethnic groups with forms of community life that have been thoroughly studied from different perspectives. However, neither has been analyzed their point of view of alterity or their relation with those who do not belong to the community. In their museums the history of the community is represented, self-images and other people's images are constructed and spread. The interesting part of these stories is not what they say but what they do, the form in which contents are expressed. These communitarian historical museums tell about the past but they mainly have an impact on the present. Like national or even imperial museums, Welsh and Mennonite museums tend to naturalize a particular self-centered, prejudicial and evolutionist point of view that often excludes other perspectives, especially those elaborated by the neighboring indigenous communities. In contrast, we believe it is necessary to take a stance for democratic, horizontal relations between communities and more polyphonic and responsible historical representations.