In a surprise to no one, ex-Facebook workers attest to distorting its "trending topic" feed.  From the Federalist:

Not only did the company suppress news from conservative sources, but it also suppressed news about topics like Chris Kyle, the former Navy SEAL who was killed in 2013, Wisconsins John Doe probe into Scott Walker, and IRS official Lois Lerners targeting of conservative groups.

That same curator said the Black Lives Matter movement was also injected into Facebooks trending news module. Facebook got a lot of pressure about not having a trending topic for Black Lives Matter, the individual said. They realized it was a problem, and they boosted it in the ordering. They gave it preference over other topics. When we injected it, everyone started saying, Yeah, now Im seeing it as number one. This particular injection is especially noteworthy because the #BlackLivesMatter movement originated on Facebook, and the ensuing media coverage of the movement often noted its powerful social media presence.