Live by the sword, die by the sword.

During the presidential campaign, Donald Trump exploited half-truths and uncorroborated Wikileaks information with reckless abandon to create in the public's mind an image of a "corrupt Hillary" Clinton. "Lock her up!" was the response these half-truths provoked among his supporters.

Earlier, Trump had led a nationwide campaign to undermine President Barack Obama's legitimacy by asserting Obama was not born in the United States. The charge, as Trump now acknowledges, was baseless.

Now, suddenly, Trump is outraged by "fake news." This week he became the victim of those same destructive and unfair tactics. Various reporters have obtained documents containing unsubstantiated allegations that Russian intelligence had collected compromising personal and financial information about Trump, possibly subjecting him to blackmail.

Responsible members of the mainstream news media didn't report it. Why? Because it came from a single source — a former British intelligence agent who had performed background research for Trump's Republican and Democratic opponents. Lacking an independent second source to corroborate the allegations, reporters and editors did the right thing and withheld it from publication.

Late Tuesday, CNN accurately reported that both Trump and Obama had been briefed by U.S. intelligence officials about the existence of these allegations. CNN also offered the rough outlines of what the uncorroborated allegations were. CNN walked up to the ethical line but didn't cross over.

The online news service Buzzfeed then opted to publish the entire, raw report from the former British intelligence agent, as if to say: Let the public decide if it's true or not.

That's not how reputable news organizations operate. Our code of ethics requires corroboration from two independent sources. We don't report rumors and innuendo. Buzzfeed absolutely crossed the line and deserved the public condemnation it has received.

These reports come in the context of a president-elect having repeatedly praised President Vladimir Putin and advocating closer ties with Russia despite warnings from his fellow Republicans that Putin cannot be trusted. The unfair suggestion of blackmail could haunt the Trump presidency, just as Trump's "birther" campaign harmed Obama's legitimacy.

Trump finally understands the devastating unfairness that misinformation can have on people's reputations and political fortunes — but only because he's now the victim. In his news conference Wednesday, he still didn't seem to understand why the spread of information hacked by Russian intelligence and published via Wikileaks was so unfair to Clinton.

But Trump does appear to understand the difference that time-honored, responsible, ethical reporting standards can make.

By continuing to hide his tax returns, evade press pools and undermine legitimate news coverage, Trump only emboldens the irresponsible practices of online newcomers like Buzzfeed. The measure of good reporting is not whether you agree with it or not. It's whether it's accurate and verifiable.

REPRINTED FROM THE ST LOUIS POST DISPATCH