… and not that other stuff. That’s effectively what Facebook provided, according to “news curators” who had worked there and were interviewed for a Gizmodo article. The effect was to put a thumb on the scales of public opinion, biasing it toward promotion of liberal views and suppressing material that might have reflected conservative opinion, or so was the article’s point.
And that point would be quite plausible when you have an unchecked system that relies upon promotion of articles by people who are drawn from a pool that itself is dominated by certain views. Selection bias nuances the choice of curators, and the curators thus bias the messaging by what they choose to promote. How do they recognize a likely article? They’ll see it when they know it.