The Age of Exploration (non-narrative)
As the empires of each race warred amongst themselves they all came to possess a generally fascist ideology where fear of the alien and unchecked nationalism were pushed in order to motivate the populace towards action against their neighbors and against foreign territories. There was at this time a general repression of learning and the history of each race was revised to promote the fascist ideology of the state. Each empire claimed to be the inheritors of old tradition and of old empire and of a right to the stars. Most claimed that their ancestors and their ancestors alone had been responsible for the creation of the laser canals and that cultural decline was to blame for the state of their empires.
The early Ethnostate Wars were largely that of consolidation and unification, with major empires seeking to crush and subjugate their neighbors with a preference towards subjugation of neighbors who were of the same species as them rather than extermination of the alien. It is possible that at this time there were many smaller polities and states which were multicultural but the revisionist historians of the time appear to have worked to remove evidence of such things so the extent to such multicultural polities existed can not be determined with any accuracy. Propaganda of the time does depict multicultural civilizations but only as a hypothetical and exaggerated warning to discourage fraternization.