^
The Star Wars films, and some of the additional material, are a bit more complicated than that. At a basic level the Jedi are good and the Sith are evil, but we've seen the Jedi go along with a corrupt Republic in the prequels, defend law instead of justice (as when Qui Gonn refuses to free both Shmi and Anakin in The Phantom Menace) and sign on to lead the Clone Army (after Mace earlier declares in Attack of the Clones 'we're keepers of the peace, not soldiers'). The Jedi seem to have no problems with the idea of cloning or cloning massive numbers of people to be used as soldiers (slaves) either. And when Anakin reveals the truth about Palpatine in Revenge of the Sith, Mace leads a group of Jedi Masters to remove him from power and though Mace does say he will let the Senate decide Palpatine's fate, he has six lightsabers on the man and the threat of assassination is clear. So basically the Jedi did attempt a coup. And from what we've seen that many in the Republic/Empire so readily accepted that the Jedi could attempt a coup is a sign to me of how ambivalent many people must have felt about the Jedi (it also didn't help that Dooku, an ex-Jedi, was leading the Separatists too).
In later (now non-canon) books the Jedi also did participate in a coup of the Galactic Alliance.
And we have seen the Jedi run away, in both Revenge of the Sith, the original films, and now with the new round of films. We've also seen how the Jedi disconnect from the people they are supposed to be protecting. How they take babies away from their parents, how they are cloistered in their nice little tower, how they forgo attachment. And even the idea of accountability. The Jedi are accountable to very few, and that itself could lead to abuse of power. The films didn't show really show that (the novels and comics I think did more so, with the use of the Dark Jedi), but the potential was and is there.
The films have less complicated when they portray the Sith. They are generally just evil. And the other material I've seen is pretty much the same. Though the non-canon novels could be a little different at times. I think the Del Ray novels were toying with the idea that Palpatine took over because he foresaw the Yuuzhan Vong invasion and Lumiya tempted Jacen Solo to turn Sith by presenting the idea of a more noble kind of Sith, and referenced Darth Vevictus, a Sith who died peacefully in his bed, surrounded by loved ones, a Sith who wasn't a madman. Unfortunately that book series didn't stay true to that and turned Jacen into a cackling madman, but I thought the idea was very cool, a Sith that wasn't a megalomaniac, but a person who was using Sith principles in an attempt to bring order to the galaxy.
