I don't think you have correctly rendered the relationship between palpatine and the rebellion. Palpatine set up the rebellion in Episode II so that he invoke the clone army--and in Episode III call for greater powers and sweep aside the republic. It was a plan that was already 10 years in the making when episode II starts since palpatine arranged for the original clone warriors 10 years before. Remember palpatine is the other bad guy whom we don't see in episode I and papatine winds up being the emperor in later episodes.
I agree with you, Lucas is telling us a story about a shady operator who uses loose tales of rebellion and ill-defined threats to obtain sweeping powers carelessly granted. Did you notice that the senate resolution granting Senator Palpatine an office very similar to Napoleon's "First Consul" and the extraordinary powers voted by the Roman senate to e.g. Pompey, and later Caesar and his successors, is offered in the film by the offensively vapid clown-character, JarJar Binks? That
could be taken as a jaded comment on the mental maturity of governance in Third World banana republics.
As for the observation that "it's only a movie", movies have partially supplanted books as a medium for discourse. And keep in mind that you could have said, 110 years ago, "it's only a book" about Das Kapital.