The debate about fact-checking the debates reached a new low on Sunday morning.

On CNN, "Reliable Sources" host Brian Stelter asked Janet Brown, the executive director of the Commission on Presidential Debates, whether moderators should fact-check candidates. (Disclosure: I am in favor).

Her response is quoted below (emphasis mine).

I think personally, if you start getting into fact-checking: what is a big fact, what is a little fact?

And if you and I have different sources of information — does your source about the unemployment rate agree with my source? 

I don't think it's a good idea to get the moderator into essentially serving as the Encyclopaedia Britannica.

Although deciding when moderators should step in to fact-check and when they should let something slide is a difficult question without an easy answer, the second part of Brown's argument is astonishing.

Some topics are too nuanced for an instant fact check on the debate stage. This probably includes President Barack Obama's definition of the attacks on the U.S. consulate in Benghazi, the subject of an impromptu fact check which landed then moderator Candy Crowley into trouble in 2012. Explaining what happened and when in these instances may require several video clips and distract too much from the debate.

But the unemployment rate, surely, is among a handful of indicators whose overt defiance on the debate stage should warrant intervention from the moderator.

Of course, there are many ways to measure the health of the labor market: wage levels, the proportion of young people not in employment, education or training or the overall employment rate. The unemployment rate itself could be deemed a restrictive measurement of the underlying problem.

But if a candidate says the unemployment rate is 42 percent rather than roughly 5 percent, viewers ought to be warned that they just heard a bogus statistic.

This isn't a preposterous scenario, by the way. Donald Trump has made precisely such a claim in the past.

If candidates bring different sources to bear on the same fact, that doesn't mean they are both right.

In an email to Poynter Sunday, Brown said her reference to unemployment "was a hypothetical. It got interrupted."

Sunday's appearance aside, much has been made about false equivalence in the media in recent weeks. The argument that two different candidates should be treated differently is a difficult one for many to accept, with good reason.

But there is a more dangerous false equivalence implicit in Brown's words: disagreements about measurable, if still flawed, indicators. Debate moderators shouldn't allow "many people say" or "I heard" to be treated as equivalent to the Bureau for Labor Statistics.