If Facebook facilitates and amplifies the messaging of the people originating the speech that leads to genocide, they're partially responsible for genocide themselves.
No that's not how this works they would still be committing criminal acts without Facebook. In most cases such genocide is almost always driven by government forces that then look the other way and act like they don't get what's happening. Governments want to blame Facebook a foreign third party simply because the government either supports the genocide and let's it happen or the government has lost control and wants to maintain the appearance that they still run the country.
What's great about China, is that it's wilfully crippling it's own economy in so many ways with various clampdowns. This is a good thing for the US, because the US has appeared impotent to counter Chinese growth and influence in the last two decades, and the bad things that come with that - i.e. Chinese support for dictatorships globally.
But the good news is, Xi's ego is sufficiently large that he's willing to undo the Chinese threat all by himself. Chinese tech had reached the pinnacle of being able to go toe to toe with US tech, Huawei was leading with 5G, TikTok has overtaken Google, gaming in China has grown massively, Alibaba was the only real global competitor to Amazon. Then along came Xi and flushed it all down the drain because he perceived it was becoming big enough to be a threat to his power as a dictator.
This is the most accurate assessment of what's going on and Xi is one of the worst leaders in the ancient and modern history of China. At least in the free world we can limit the damage by voting out our Trumps or their term limits limit the damage. People don't realize how much innovation in technology comes from video games and how network effects affect other industries. GPU development was and still is driven in large part by video games which are useful in other fields such as medicine or computer vision. Machine learning is pushed forward by social media companies. Even if China puts a huge effort in trying to develop their hardware and software industries they're still decades and generations behind. Central state planning cannot produce the innovations that a decentralized market system can this is known already. These clampdowns make catching up even more difficult if not impossible.
"Turn on, tune up, rock out." -- Billy Gibbons