>I'm guessing that colluding with China to break international human rights laws is not protected by a contract as it's illegal in the USA and likely illegal in the UK

The wikipedia article says facebook tried to appease chinese censors. That's bad, but so far as I can tell, isn't illegal under US or UK law. Microsoft complies with chinese censor demands for bing and they seem to be doing fine, for instance. The only plausible case for "they're breaking laws" is them breaking the UDHR, but that's an unenforceable document that's not worth the paper it's printed on.