On Facebook, Scott Rafer writes: 

"I've been trying to rationalize Mark Zuckerberg's behavior, and all I can come up with is that he is secretly pro Trump. He can't admit or too much of his workforce would quit starting with Sheryl Sandberg. But the behavior around defending Peter Thiel and denying the influence of fake news and Facebook's place in it only leads me one place."

My response

Imho it's "more complicated." 

He has to work with the new government, and if they're going to act like Russia or China, they're going to want to control what people say on Facebook. Zuck has been trying to work with China, so he knows all about this, far more than any of us. 

Presumably Facebook in their negotiations with China has had to demonstrate the ability to control speech. Those features would not be turned on in the US, but Trump might want them to be, at some point. The excuse will probably be something like preventing terrorists from using Facebook to plan attacks, but it's likely it would be used to control dissent and keep the opposition disorganized and confused. His supporters too, for that matter. 

Facebook is likely already communicating with the new administration, since they absolutely understand how powerful Facebook is. Of course they are even more powerful (Trump et al). So he has to be careful. 

Facebook can thrive, for the time-being, without being in China (as they are), but they probably couldn't survive without the United States. He almost certainly is not in favor of Trump personally, from what I know about him, but if he were to act on that, or if it could be spun that way, it could be a disaster for his company.