It was dumb because they were no match for him. He was older, more powerful and more skilled. Make no mistake EVERYTHING that happened in that room was calculated. The Emperor could have killed Mace without Anakin. He just wanted Anakin to see how the council bends rules when it benefits them.
Mace and Yoda are Palpatine's equals and Mace had the drop on Palpatine as soon as he smashed the windows. If Palpatine was just interested in forcing Anakin's hand he wouldn't have tried to kill Mace in front of him.
Look at the videos from
@Atsym Sknyfs .
Anakin walks in
before Palpatine tries blasting Mace, that's why it's not the case that Anakin believes Mace has evil intentions. He walks in and hears this:
"You are under arrest, my lord
"
"No no you will DIE"
When Episode III came out this was a huge debate, and George had to step in
twice to clarify that Mace is Palpatine's equal and legit got him. Palpatine starts faking it
after failing to kill Mace. From the words of the God himself:
In the The Making of Star Wars Revenge of the Sith, George Lucas, the creator and ultimate authority regarding the Star Wars universe, responded to the question of whether Mace Windu brought a weak group of Jedi with him for the confrontation with Palpatine by replying that "one would have to be either Windu or Yoda to compete with Palpatine," and that if Anakin had suffered none of his injuries, he could have beaten the Emperor
George in the DVD commentary:
"this scene begins with Mace overpowering Palpatine. Palpatine feigns weakness when he realizes Anakin isn't there to help Mace Windu, he came to stop him.... Initially Anakin was there from the start. I changed it so that he didn'thave enough time to think, and to make Sidious a bit more slimey"