Alright, this is slightly spoilers from the planet Voss, but it answers your question:
The lines of good and evil are blurred. To put it simply, the Sith are actually the victims in this entire scenario and are striking back at their oppressors. Years ago, the Jedi persecuted a crusade against the Sith. They razed the temples of Korriban and Dromund Kaas, as well as bombing both planets.
The Jedi chased the fleeing Sith across the galaxy to Voss, where the 'good guys' corrupted half of the race there into the Voss. Corrupted part of the land into a land filled with darkness and evil. And set the inhabitants of the planet against one another in an endless civil war filled with blood...
-All to capture and kill people who disagreed with their religion-.
To put it simply, evil and good are based on perspective. This is true no matter what. In the Empire my character was hailed as a hero by the Imperials as well. I'm sure Jedi are hailed by the Republic as heroes.
But in that spoiler? Pretty much confirms who the real bad guys are.