The Rebels Are The Bad Guys - To The Ewoks
Yes, the destruction of the Death Star and the collapse of the Empire is a good thing for the galaxy as a whole, but it has no effect on the Ewoks and their way of life in particular, and it's certain that the Ewoks paid too high a price for a victory compared to the possible extinction of their species.
I have heard some speculation about the Imperial-Ewok relationship on the Star Wars Minute podcast: did the Forest Troopers even know the Ewoks were there? Did they treat the Ewoks like troublesome raccoons? To bolster the Ewoks motivation for enter the conflict, they could have shown the Empire clear-cutting the forest to make space for their deflector shield, or maybe an AT-AT crushing their habitat? As it is in the movie, C-3PO tells stories of the Rebellion, and the Ewok leader spontaneously volunteers his people to fight.
FUN FACT: I saw this Special Edition in March 1997 - The Phantom Menace was coming in 26 months!