Facebook already makes choices about what it does and does not promote on its platforms.

This is nothing like a government ordering the imprisonment of a section of its populace.

The underlying logic of the reporting blaming Facebook for the Rohingya genocide is that Facebook somehow has more power than a totalitarian, genocidal military dictatorship. Given that assumption it's hard to see why we shouldn't also treat any restrictions they place on speech in the same way as we would a totalitarian government.

I disagree. I think the underlying logic of the reporting blaming Facebook is that it was used as a tool to foment hatred against the Rohingya minority in Myanmar. Both the statements “The Myanmar government is waging genocide against the Rohingya minority” and “Facebook doesn’t have a complete grasp of what its platform is being used to accomplish” can be true.

Sure, because removing a facebook post is the same as imprisoning people.

But let me go to fb and start advocating hate against republicans, I'm sure they will agree it's all part of my free speech rights.

No. This is hyperbole. There can be a formal difference, e.g. in terms of transparency about the rules that are upholded and the instances where they have been applied.

This is a very strange comparison to make when there was an actual genocide against muslims with Facebook's current permissive content policy. With slightly more editorial control against stoking ethnic hatred, thousands of people wouldn't have died in a genocide, but exercising that editorial discretion on Facebook posts is akin to rounding up the uighurs?

Why do you value the ability to broadcast (not speak, but have amplified) incorrect statements above hundred of thousands human lives?

And why do you compare restrictions on physical freedom of people in China to some kind of reduction in the reach of statements by powerful figures in Myanmar?