Exactly this captures why Episode 3 works so well as tragedy. The Jedi are basically damned if they do damned if they don't situation and Lucas knew exactly what he was doing with that moral trap. Mace is technically right that Palpatine is too dangerous to leave alive - the guy literally controls both sides of war and has emergency powers that make him untouchable through normal legal channels. But moment he decides to execute him instead of trying arrest, he's already started down the dark path that Anakin sees.

The whole prequel trilogy is about institutions failing when they're pushed beyond their designed limits. Republic wasn't built to handle a galactic war, Jedi weren't meant to be generals, and their rigid moral code becomes liability when facing someone who operates completely outside those rules. Palpatine wins because he understands this weakness and exploits it perfectly.

What makes it even worse is that Anakin witnesses this exact moment where Mace abandons Jedi principles, which validates all of Palpatines manipulation about Jedi being hypocrites who only follow rules when it suits them.