The Separatists did not become the Rebellion. Tattoine is in the outer rim of the Republic. Liberty dying was a reference to the usurpation of power from a duly elected democratic body body, the Senate, which represented the populace by the Emperor, which led to the eventual complete dissolution of democratic representation by the time of the battle of Yavin. Much as with the revaluation of the Confederacy I think context and content is important. For one the Confederates are on the wrong side of history because they supposedly fought for freedom... THE FREEDOM TO OWN OTHER HUMAN BEINGS. Period. So too with the Empire. They are a metaphor for any oppressive system of government that is impervious to the will of the people because the people have no actual input, read free elections, to voice their opinion.
The Republic is a stand in for any/all democratically minded republics. Such entities are messy, imperfect and unsatisfactory to all because they are based on compromise and the respect of majority rules while ensuring minority rights. Again, this is imperfect and leads to less optimal outcomes. And the idea was that the Republic had become sclerotic and yes, there were signs like being unable to enforce the rights of people like Anakin's mother in the Outer Territories, that pointed to problems in the system of the Galactic Republic. But that doesn't make what the Emperor did the proper solution nor does that absolve the Empire of responsibility of it's crimes in imposing a new order which did nothing to address the failures of the Republic. The "dream" the Rebels fought for was the restoration of a democracy within a republic.
More importantly though... Shouldn't this be something for the STAR WARS forums proper?