FB uses algorithms to determine which news items to present to you and how prominently and frequently they get presented. It would be very easy to privilege political news items that had a certain ideological slant. After all, that's what the NY Times and Rush Limbaugh do. And FB has already admitted manipulating news feeds for its own ends.
Zuckerberg is a very actuve, engaged liberal. And like Gates and all the other techno nerds he's in search of meaning and significance in his life. Watch out.