But here's the thing about the Sith though, they tend to view "My chains are broken" as "Everyone else is wearing them under my heel." Not all who follow their passions are evil, yes, but the Sith use them for evil goals. Grated their are probably Sith who don't, but that nuber is so insignificant compared to those who do that it can be generalized that the Sith Order as a whole is evil.