Saying that his taking the Praetorship meant that he'd "won" is as ridiculous as saying that African Americans aren't still oppressed just because the President is black.
Why would anybody compare that? Shinzon is closer to a dictator than an elected official. Now you're just reaching since simply saying "I have a blind hatred and that's that" is tougher to admit.
It's really quite simple from a storytelling perspective (and also fictional, the politics of Star Trek have never been close to realistic, maybe that's what makes it difficult for some people? That whole FICTION thing? I dunno).