Mark Zuckerberg didn't write this. Facebook does this thing where they make it seem like it has one voice speaking for them - which is Mark. What is happening is multiple people in Facebook's PR department wrote this. I would even argue the title is misleading. We're feeding into the frenzy that Mark is writing this on behalf of Facebook. We should say it like it is. "Facebook released a statement"
This reminds me of Big Brother, or (perhaps more appropriate) The Wizard of Oz. It is always more than a little creepy to encounter a digital simulacrum that is actually a group effort.
The President has almost never written his own speeches, and yet we don't say they're written by his speechwriter. We say "The President delivered a speech."
Mark certainly signed off on this post, or at least on the people who wrote it. Why should we treat it any differently than when any public figure "says" something?
Facebook is done. It won't even need replacing. People are realizing its not worth the trouble.