During the time I was managing editor and then executive editor of The Washington Post, from 1984 until 2008, plenty of allegations flowed into our newsroom about candidates for local and state offices, Congress and the presidency. They involved everything from corruption to conflicts of interest to sex lives. Quite often, we knew they also had been circulated among other news organizations and were the subject of widespread gossip in Washington, as was the case with the Trump dossier.

In many cases, we found after exhaustive reporting that the allegations were false or unverifiable. My rule was that we would publish only what could be verified, even if we suspected it was true or thought someone else might publish it anyway. Most of our competitors followed the same professional and ethical standards, and they still do.

This was also the case with the Trump dossier, which was an open secret among reporters in Washington. Many news organizations tried and failed to verify its contents and declined to publish anything about it. That changed when CNN accurately reported that a classified report summarizing the dossier had been given by intelligence officials to President Obama, Mr. Trump and congressional leaders. Then BuzzFeed posted the entire dossier, even while telling readers that the “allegations are unverified, and the report contains errors.”

This led Mr. Trump on Wednesday to call BuzzFeed “a failing pile of garbage” and denounce CNN as a “terrible organization” and “fake news.” This is a dangerous road that Mr. Trump is heading down, mashing together, in a sweeping complaint, CNN’s conscientious approach with Buzzfeed’s ill-considered action.

At a time when the president-elect is trying to make major political changes in a deeply divided country, he is encouraging the public not to believe reporting by responsible news organizations that are striving to hold the government accountable. He did the same thing during his campaign, rallying his followers against the “dishonest media” while at the same time feeding news organizations and the public distorted and unproven allegations about his opponents.