Same could be said of protesters standing by watching looters. It's not so cut and dry. Good people get put into terrible positions when things are this nuts.
I get what you're saying, but I have to wholly reject this comparison.
Joe Blow protester in the street not putting themselves in harm's way to physically stop violent protestors and/or looters is in no way equivalent to someone who's sworn & paid to uphold the law standing idly by while one of their fellow officers hurls a non-violent 75 year old to the ground & cracks his head open on the pavement. Same goes for every one of those officers who witnessed what happened, and didn't say "boo" when the official report was written up as "he stumbled and fell".
I appreciate that it'd be hard to go against the grain when it comes to your fellow officers, and even harder when it comes to your superiors. But that's a fundamental part of your job description. And there sure aren't a lot of jobs out there where you'd be employed for long if you declined to perform the basic reason for your employment because it's too hard.