TOG's long and continuous history of conquest has brought many divergent races and cultures into the Empire. Some, like the Ssora or the Zog, have been found compatible or malleable enough to be integrated with some indoctrination and cultural re-programming. Others are trouble. Strong ethno-centric cultures like the Gaelic Confederation or races with a powerful sense of racial and cultural identity like the Naram might serve as a rallying point for anti-TOG sentiment. The government's strategy to suppress and eliminate these tendencies is the Diaspora.
A people scheduled for Diaspora is distributed across TOG space in isolated groups that are too small to present a viable gene-pool or social kernel able to resist the pervasive cultural influence of the Empire, and so are doomed to slow extinction. In the case of human or near-human (Naram) societal groups, the children of influential families are placed in "exchange programs" and enticed to enlist in Imperial institutions such as the Civil Service schools, the Navy or mobile Legions where they are kept at a distance from their home society, heavily indoctrinated and estranged from their parents' ways.
From TOG's viewpoint, the Diaspora is preferable to genocide in many ways. It is a largely non-violent form of cultural murder. Re-settlement is also harder to resist or view as a hostile act, and creates no martyrs. Most peoples subject to Diaspora do not realize what it is doing to their culture, identity and way of life until it is too late. Some even eagerly participate, being promised new planets to settle or embracing re-location as a way to escape poverty or participate in the greater Empire. The Lictor's propaganda machine is very adept at putting a positive spin on the first steps of Diaspora. It is hard for Renegade agents to foment resistance against what is presented as a benign act of the Empire toward the people in question.