Why do the Jedi hate the Sith so much? Anytime a Sith says "Hello. My name is Darth Evilface", the Jedi either try to redeem him, or fight him (and kill him). If the Jedi really wanted balance, they'd leave the Sith be, or at least keep them away from their area (they get part of the galaxy, the Jedi get the other part). Perfect balance.
Throughout canon, whenever the Jedi win, they say the Force is in balance, when it isn't. In fact, it's far from it.