Mark Zuckerberg, the company’s CEO, has now said that in an internal investigation, the company could find no evidence of story suppression. And in some ways, you could see the company’s editorial hand in “Trending” as part of its longtime emphasis on distributing “high-quality content.”

But we might know more later this month. Senator John Thune, a Republican of South Dakota, has formally asked Facebook to answer questions about its neutrality in running the feature. Company representatives have also been asked to meet with staff from the Senate Committee on Commerce, Science, and Transportation.

Senator Thune made those requests in a letter to Facebook—a remarkable document that it’s worth spending some time with. That’s because, before asking specific questions, Thune raises the following concerns:

[W]ith over a billion daily active users on average, Facebook has enormous influence on users’ perceptions of current events, including political perspectives. If Facebook presents its Trending Topics section as the result of a neutral, objective algorithm, but it is in fact subjective and filtered to support or suppress particular viewpoints, Facebook’s assertion that it maintains a ‘platform for people and perspectives from across the political spectrum’ misleads the public.

This is an fascinating implication. Facebook has said it is a platform for perspectives from “across the political spectrum,” but it specifically never has claimed that it will give all those perspectives equal weight. It promises that it will give everyone a place for their ideas, but not that it will be particularly fair about it.

Yet just by talking about misleading the public, Thune is presuming an incredible thesis: that in order for Facebook to make space for all viewpoints, it must be balanced. Which is funny, because Thune has gone on the record a great deal about the role of a government official in regulating media fairness. From the mid-2000s to its eventual repeal in 2011, Thune was one of the lead critics of the Fairness Doctrine, a requirement from the Federal Communications Commission that broadcast stations present “controversial topics” in an honest and balanced way. In fact he often advocated for its repeal (even though it was overturned by the courts in the 1980s).

“Our support for freedom of conscience and freedom of speech means that we must support the rights granted to even those with whom we disagree,” Thune said in June 2007. “Giving power to a few to regulate fairness in the media is a recipe for an Orwellian disaster.”

He elaborated on those views in an article for RealClearPolitics. “I know the hair stands up on the back of my neck when I hear government officials offering to regulate the news media and talk radio to ensure fairness,” he wrote. (The FCC formally repealed the Fairness Doctrine on its own prerogative four years later.)