Good points, the Terra Prime folks have been a minority as they would have been able to influence politics otherwise.
I think Samuels is basically the character that R. Star wants. Sure, the time frame (Samuels already learned his lessons when the story beings) doesn't match but it is again a question of atmosphere and not of stupid literal reading. Samuels' biography mirrors the story of the species. There are some demons from our past who sometimes reemerge (think about the fictional historical WWII/eugenics background that influences this episode, Khan, TNG's pilot, Bashir and so on; sometimes the historical toilet comes up) but for the time being we defeat them.