Ok here we go again. Unless Disney is completely ignoring everything to do with the Jedi that Lucas set down, balance does not mean equal!!! Lucas said that the JEDI believe balance is the universe being completely under the influence of the Light Side. When the Sith are destroyed, their influence over the Force is gone so it's in balance. Again from the JEDI's point of view. It doesn't mean the Dark Side is gone, just that it doesn't hold sway over the galaxy. It has absolutely nothing to do with the sides of the Force being equal or ying/yang or whatever else. If that were true there's no way the Force could be unbalanced by two Sith. Think about it.
Balance is equal parts Light and Dark. That's everywhere in Star Wars.
Mortis Yin-Yang, balance is the middle between Light and Dark.
Mortis gods, balance is between the Light and the Dark
"Prime" Jedi, equal parts Light and Dark
And George had been saying that balance is both Light and Dark.
- "The overriding philosophy in Episode I—and in all the Star Wars movies, for that matter—is the balance between good and evil." -George Lucas, quoted in L. Bouzereau, Star Wars: The Making of Episode I, 1999
- "In each of us we to have balance these emotions, and in the Star Wars saga the most important point is balance, balance between everything." -George Lucas, TimeMagazine article, 2002
- "The idea of positive and negative, that there are two sides to an entity, a push and a pull, a yin and a yang, and the struggle between the two sides are issues of naturethat I wanted to include in the film." -George Lucas, quoted in L. Bouzereau, Star Wars: The Annotated Screenplays
- "The Force has two sides - [Light and Dark]. It is not a[n inherently] malevolent or a benevolent thing. It has a bad side to it, involving hate and fear, and it has a good side, involving love, charity, fairness and hope." -George Lucas, Times Magazine, 1980
- "I wanted to have this mythological footing because I was basing the films on the idea that the Force has two sides, the good side, the evil side, and they both need to be there. Most religions are built on that, whether it's called yin and yang, God and the devil—everything is built on the push-pull tension created by two sides of the equation. Right from the very beginning, that was the key issue in Star Wars." -George Lucas, Times Magazine, 2002
No way the Force could be unbalanced by two Sith? Yet that's exactly what we see. When Yoda says that they[the Jedi order] was blind to not sense the creation of the Clone army. Mace suggests that they should inform the Senate that "our ability to use the Force had diminished." Wait why? Yoda answers that at the end of the film. "The shroud of the Dark Side has fallen." Two* Sith Lords had swung the balance of the Force so out of whack, that the Jedi couldn't tell they were sitting 10 feet away from Dark Lord himself.
*technically it's many groups of Sith over a 1,000 years, plus there was a Sith shrine under the Jedi temple.