Remember : - It all started with Facebook being accused of manipulating the timeline to remove conservative stories during the campaign - At the time, their PR was along the lines of : we will fire the staff and replace it with an "objective" algorithm - Shortly before the end of the campaign, the Fake News narrative started to be tested under various forms ("conspiracy theories are going mainstream", "damaging rumor…
This has nothing to do with the bill of rights. Facebook is not the government, government is not requiring fake news to be censored, and the fact checkers are independent organizations.
You don't have an inalienable right to spread whatever political lie you want to millions of people. Facebook is this era's nightly news and, just like the nightly news, they have a right to avoid sharing crazy conspiracy theories and outright lies.