They are realists and believe "Peace is a lie" that is pretty much a fact is there will never be peace unless you defeat all of your enemies. They embrace Darwinism. People are either made stronger through their trials and experiences or they remain weak and the weak are either delt with or they die on their own because they are fails and cant handle their trials. Again this is good. There is no place in society for the weak and worthless as they only make society as a whole weaker. So why are the Sith and the Empire as a whole considered bad? Also the whole comparing them to Nazis isnt exactly fair. The Sith dont discriminate against anyone, well other than the weak and useless. Everyone is given a chance to prove themselves useful.