The run up to the US elections are proving to be somewhat controversial and hugely divisive. There's a heightened degree of sensitivity that is spilling over into some interesting areas.
Take the complaints about Facebook allegedly filtering conservative news in support of an alleged left-leaning political bias. The evidence isn't actually completely solid although there are indications it's not far from the truth.
Does that make Facebook any different from any other media organisation reporting the news today? No, it doesn't. Take your pick from any news source available to you now and show me one without a hint of bias. It can't be done, even allowing for different ownership, management and funding that themselves practically guarantee that a publication will demonstrate a lean in one direction or another, each and every article 'benefits' from the author's own bias.
Even the BBC, for which even-handed reporting is enshrined in its articles of incorporation, is regularly accused of favouring one side or another of the UK's political landscape.
Yes, Facebook's trending topics are pulled from other organisations based on what's in the news and, yes, it would seem that it favours sources which are themselves considered to be left-leaning, but no, it isn't a problem. Unless you intend to remove political bias from every reporting stream out there (and god luck with that) Facebook should be allowed to put its own take on what is important without outside interference or condemnation.