The Washington Post has fallen into the habit of accusing Bernie Sanders of misleading the public even in cases where the evidence is strongly on the side of the Vermont senator. Back in July, Post fact-checker Glenn Kessler objected to a statement Sanders made in the first debates in the Democratic presidential primaries: “Three people in this country own more wealth than the bottom half of America.” Kessler acknowledged that “this snappy talking point is based on numbers that add up.” But then he added that “it’s also a question of comparing apples to oranges.” According to Kessler, it makes no sense to compare rich apples like Jeff Bezos (who own real capital) with millions of poverty-stricken oranges (who possess only debt). In Kessler’s words, “people in the bottom half have essentially no wealth, as debts cancel out whatever assets they might have.”

Kessler’s puzzling rebuttal drew much criticism, including sharp words from John Nichols of The Nation. Simply on logical terms, it’s hard to understand why one should exclude the poor from comparisons with the rich simply because the poor have debt rather than capital. Indebtedness combined with a lack of assets, after all, is a big part of the condition of being poor. By Kessler’s reasoning, it’s impossible to compare the rich with the poor at all.

Last Wednesday, the Post took issue with a Sanders tweet that stated, “500,000 Americans will go bankrupt this year from medical bills.” The fact-checker acknowledged that Sanders was providing an accurate gloss on some of the scholarly literature on this topic, including an editorial from the American Journal of Public Health (AJPH). But the fact-checker claimed that the “AJPH editorial did not undergo the same peer-reviewed editing process as a research article.” This assertion is misleading: The editorial was appropriately peer-reviewed.

The gravamen of The Washington Post’s fact-check is that there is another scholarly article that gives a lower number than 500,000 medically induced bankruptcies. But the Post’s preferred study differs on methodological grounds that are themselves shaky and contestable: The study takes an extremely narrow view of causation and counts only people whose bankruptcy was “caused by a hospitalization.” It only takes a moment’s reflection to realize that there are many other ways that medical debt can accrue aside from hospitalization, including loss of income. The AJPH editorial is on firmer ground in recognizing that people who suffer from health problems are likely pushed into poverty by multiple interconnected factors that are not in reality separable.

As with the earlier fact-check on inequality, The Washington Post is trying to use fact-checking as an ideological weapon. Sanders is under attack not for making false statements, but for calling attention to facts that are politically unpalatable for those who are happy with the economic status quo. It’s unclear why the Post so often goes after Sanders in such a myopic fashion: The paper denies that its coverage is influenced by billionaire owner Jeff Bezos, but institutional bias can be more subtly grounded in factors like the economic class of the editors or the newspaper’s being embedded in elite Washington culture.

With these polemics-disguised-as-rebuttals, the Post is discrediting the entire journalistic genre of fact-checking. This is dangerous in a way that goes beyond any damage it does to Sanders as a presidential candidate. In truth, Sanders has little to worry about. The fact-checks are so ludicrous that they are unlikely to sway any voters. What they are more likely to do is feed into a pervasive distrust of the mainstream media, which is bad for democracy.

Fact-checking is an essential journalistic service, all the more so under President Donald Trump. As is well known, Trump is a pathological liar on a scale never seen before in American politics. He makes Richard Nixon and Joseph McCarthy look like Boy Scouts. Many journalists, notably Daniel Dale of CNN, have done a commendable job in keeping track of Trump’s unending Niagara of prevarication, fibs, invention, and nonsense.

Trump himself worries about the danger that the media will hold him accountable, which is why he mocks fact-checking. On Monday, he tweeted, “The LameStream Media has gone totally CRAZY! They write whatever they want, seldom have sources (even though they say they do), never do ‘fact-checking’ anymore, and are only looking for the ‘kill.’ They take good news and make it bad. They are now beyond Fake, they are Corrupt…. The good news is that we are winning. Our real opponent is not the Democrats, or the dwindling number of Republicans that lost their way and got left behind, our primary opponent is the Fake News Media. In the history of our Country, they have never been so bad!”

Maggie Haberman of The New York Times offers a useful gloss on Trump’s tweets: “A Trump adviser, who spoke on the condition of anonymity, said weeks ago that the president, whose own approval ratings have stayed upside down, needs voters to feel negatively not just about his opponents but about longstanding institutions.”

Haberman’s analysis is persuasive: Trump’s path to reelection runs through discrediting any independent institution that might hold him accountable, be it the FBI, congressional Democrats, or the mainstream media.

Unfortunately, media outlets sometimes help Trump along in his desire to tarnish them as reliable independent sources of truth. The Washington Post is doing journalism no service by turning fact-checking, which should be grounded in empirical evidence, into a tool for polemical mudslinging. We need accurate, sober, well-aimed fact-checking more than ever to document Trump’s many lies—as well as the occasional false statements of other politicians (including Sanders). Unfortunately, the Post has decided to expand the parameters of fact-checking in a way that undermines the entire enterprise.

The mainstream media has already lost the MAGA-heads who agree with Trump’s crusade against “fake news.” Now it might also lose the millions of Americans who recognize that Sanders’s presentation of economics is closer to the mark than the Post’s bizarre exercises in politically motivated nit-picking.