Well, the Sith can choose Light Side options. There have been times that I found the Light side options to be far more evil. Like the time, I brought a person's (actually a Jedi I was seeking) parents to the Empire and let them live a life of luxury. Or how about the Noble that I banished from his home, so that he lost his name, his standing, and all his money? Yeah, I could have killed him, but what's more evil, killing the guy, or making him wish I killed him?
That is pretty much Star Wars canon. The Sith always lose because they always betray themselves. Check the back story to the Empire. They almost beat the Republic centuries ago, but the Emperor's apprentice betrayed him and tried to kill him during a major part of the war. This allowed the Republic to recover and mount a counter attack pushing the Empire back to Korriban and then the Republic fleet all but destroyed the Sith Empire there.Marcus Kehoe said: