Again he is the harsh side of the light, the Paladin if you will. The man who stares the dark in the eye and says, no.
At the beginning of Revenge if the Sith, Anakin kills Dooku, who had just been rendered a non'threat after losing his hands. Immediately he regrets it, "I shouldn't have done that."
Palatine responds, "He was too dangerous to be left alive."
"It's not the Jedi way."
Towards the end of the movie, when Anakin walks in on Windu holding Palatine at saber-point, and both Jedi think (earnestly, if mistakenly) that the Sith Lord is defeated and helpless.
Windu insists that Palatine must die. "He's too dangerous to be left alive."
Anakin objects, "It's not the Jedi way."
We all know how
that ends. Mace Windu is not a paragon or righteousness. He is the man who, when pushed to the absolute brink, sets aside his ideals because they do not give him what he wants. If he is a Paladin, then he is an Oathbreaker. And in that moment, he is that straw that breaks the camel's back, the last lever that Sidious needs to bring Anakin over to the Sith utterly and abaolutely--after all, if this bastion if the Jedi Order does not hold to it's precepts, then what is the point of them?
Say what you will about the Prequels. They are deeply flawed movies. But this was well-executed. Mace Windu, in the end, embodies the failure of the Jedi Order to live up to its own ideals. He is nothing less than a failure. And I would argue that, at the end of his life,
he had fallen to the dark side. The look of absolute hatred on his face before Anakin intervenes makes it hard for me to think otherwise. That he could fall here, in this story, is entirely reasonable.
What? Just because he stands against Cameron does not make him a zealot. Cam has been doing some pretty stupid and reckless things. Hanging out with some of the most notorious Jedi haters and hunters in the galaxy. Trying to foolishly walk the knife-edge of both sides of the Force, without having even mastered one side. I would be concerned if I was in Mace's shoes, especially since they know he is susceptible to the dark side as the story has proven. Cam is also insanely paranoid and thinks the Jedi are out to get him which does not help things and further drives a wedge between them.
You're leaving out a very important part of Mace's position here. We have seen, though Cam has not, that Mace believes Cam should never have been admitted into the Jedi Order because
Revan fell to the dark side, and has from the very beginning. Because this story isn't ignoring his personal faults and failings, and is if anything accentuating them. This Mace Windu adheres to the light out of blind zealotry, and that makes him vulnerable to temptation.
Good does not need to be nice. But it does need to be principled. And when the chips are down, Mace Windu is not a man who chooses his principles. He is so sure of his own righteousness that, with the right pressure applied, he could dive headfirst into the darkness and not even blink.