The Sun Guard are said to have a religion focused on their system's star, and it's possible that the Sith ideology intersects with this. Somehow they develop a moral code that is built around competition and the pursuit of power (for solar resources?), leading to adoption of the ideology of the Sith (Power>Strength>Victory>Chains Broken). Being non-Force-sensitive, the Sun Guard could fearmonger against Force-users in general now that the Sith Lords themselves are history. Sith ideology could have appeal to non-Force-sensitives regardless. Edit: A real-world parallel from anti-Force-sensitive would be to majoritarian bigotry and discrimination. You mentioned the Holocaust, which was the end result of decades of fearmongering against a minority who antisemitic conspiracy theorists believed were somehow the overlords of society. That would be a very clear link between such a story and real-world politics. Better than the PT? Such real-world parallels would be even better than the PT's.