THE RISE OF REASON AND DISCONTENT:
The Sith (Silus and the other Founders) do not claim to be totally original in their ideas, but rather are the natural progressive conclusion of society-wide feelings and concepts.
If you watch the music video by Korn: Evolution, you will see that general IQ is decreasing, especially around the time of the cultural revolution, and has continued to decrease. The Counter Culture was brought on by outrage at the Government and likely, the falling IQ of mankind leading to greater and greater global instablity. After the fall of the Counter Culture the masses went into denial in the 80's (American Psycho,) in the 90's we bargained for a better life by buying endless numbers of new gadgets and products, and now in the New Millenium we are in depression and anger, as evident with modern media. We view the Sith as the natural outcome of a less and less controlled/stable world as well as discontent and rebellion. We are pragmatists motivated to find a solution to the dark path Humanity is taking, and put them on the Golden Path.