"When moderators at Facebook, Google, and Twitter review the appropriateness of posted content, they generally follow First Amendment-inspired principles..."

"... according to Kate Klonick, a legal scholar who analyzed the practices of the three companies in the Harvard Law Review last year. Some of the platforms’ standards are unsurprising, such as their bans on pornography and terrorist incitement. Other rules require moderators to block 'hate speech,' an ambiguous term that, despite Facebook’s efforts at delineation, can be politicized.... Facebook and YouTube have long positioned themselves as neutral platforms, akin to eBay, open to all who are willing to abide by community standards. They’ve resisted the argument that they are in fact publishers—that their human moderators and algorithms function like magazine editors who select stories and photos. But Facebook’s stance has seemed to shift recently. In April, its founder, Mark Zuckerberg, told Congress, 'When people ask us whether we’re a media company or a publisher, what they’re getting at is: do we feel responsible for the content on our platform? I think the answer is clearly yes.'  This is a be-careful-what-you-wish-for intersection; none of us will be happy if Silicon Valley engineers or offshore moderators start editing our ideas.... Practices that marginalize the unconventional right will also marginalize the unconventional left. In these unsettled times, the country could use more new voices, not fewer. From its origins, the American experiment has shown that it is sometimes necessary to defend the rights of awful speakers, for the sake of principles that may help a free and diverse society renew itself."

From "Alex Jones, the First Amendment, and the Digital Public Square/How should we challenge hate-mongering in the age of social media?" by Steve Coll in The New Yorker.