My two cents All the sith we see in the movies are evil, in this game the leadership of the sith empire are evil as well, does following the sith code or exploring powers outside of the jedi's domain require or make you evil, no. The explanation of this apparent contradiction lies in the origins of the sith. A rough quote from B5 that sums up the sith is "you're like abused children who have grown big enough to do the same thing to someone else, as if that will somehow balance the scales, it won't." The sith began as a rebellion against the oppression of the jedi code, the problem is they never lost this rebellious outlook so they never moderated themselves, never stopped each other from going to far and became more extreme and more evil as the focused on negative emotions because they were the fastest path to power. This sith in this game have all that and the fact that the jedi and republic attempted to commit genocide to try and remove them forever.