The line about Sith Lords only dealing in absolutes is intentional. Lucas said in an interview that the stark black and white color scheme of the Empire was a symbol of their extremist mindset while the earth tones worn by the Jedi reflect their view of a universe embracing change and subtle nuance. The Empire's similarity to the Third Reich shows that he meant absolute power with no room for the messy vaguaries representative democracy entails.
Lucas has obviously tired of the endless associations and theories applied to his characters. Recent advertising tie-ins actually deflate and poke fun at them. Yoda uses the Force to swipe a guy's lunch in a diner yet fails to obtain the soft drink; Vader attempts to con a winning game ticket from an ordinary Joe only to have the door slammed in his face(plate). But hey, who wouldn't love to choke out one of those anthropomorphic M&M characters? Allowing these skits seem to be Lucas' way of reminding all of us that "It's Only a Movie!"
That's funny!
My kids are interested in all the Star Wars stuff. I keep saying, "If you expect it to all make sense, you're just going to have a headache!" And my husband and his co-nerds have come up with some "business" excuse to attend the opening of Episode 3.
The other earthly souce is ancient Rome with its Republic changing into an Imperial power with Emperors and a Senate. The reference to his troops as Legions by the Emperor in Return of the Jedi is an obvious example. George Lucas has used many sources from around the world for his saga. There is a heavy Japanese influence in the costuming too. The Hidden Fortress movie from Japan is also used as another source. Old movie westerns and serials with their cliffhangers as well.