Some jedi did abuse their power. Pong Krell comes to mind when I think of that. They saw consequences for their actions. As for the Jedi order themselves, they had the best of intentions, but had a flawed and overly political system. Also, Endor could have turned into an apocalyptic frenzy I guess, but given that Star Wars isn't known for following real laws of physics (using the force, sound and fire in space, some living creatures breathing in a vacuum, etc), I would say that most likely didn't happen.
