Mr. Tapper called it an example of how he had been trying to “draw basic lines about truth and decency and trying to get answers to questions.”

As such, it was an object lesson in what doing it right looks like. At the same time, it was all very basic, what reporters are supposed to do: Ask questions of people in power and insist on answers.

But it bounced around the internet as a shining example of stand-up journalism, because, unfortunately, such moments now seem so rare — especially in a year marked by Matt Lauer’s soft interview of Mr. Trump at NBC’s “Commander in Chief” forum in September, and CNN’s own lapses with hires like the Trump aide Corey Lewandowski.

If only such moments could stop being so special and start being normal.

Television news is going to have to do its part should Mr. Trump and his administration try to make policy based on false assertions, the same way he used them on the campaign trail. (And, yes, television will have to be just as vigilant should Mr. Trump’s opponents use falsehoods to fight him, too.)

The same holds for all of the news media, of course. But live television can be a safe harbor for falsehood and deflection.

It’s easy for me to criticize as a columnist who has time to analyze and fact-check before writing. On television, in real time, even the best-prepared interviewers may have neither the time nor the facts to catch a lie and call it out. Even when they do, their attempts to call foul can turn into stalemates if the interviewee insists on continuing to forward something that’s false or unsubstantiated, which seems to be the latest craze (see Reince Priebus, millions of illegal votes, “Face the Nation”).