Donald Trump is an unreasonable man. He makes wild claims that he cannot back up. He attacks those who question him. He demands deference from his fellow presidential contenders and from the media, and in so doing he prevents the sort of freewheeling debate that is needed most when a party is choosing a nominee—and a country is choosing a leader.

But that’s not the problem with the front-runner for the Republican nomination.

The problem is that, when Trump is unreasonable, political and media elites tend to give him a pass.

Trump’s fellow Republicans are the worst. Party leaders like House Speaker Paul Ryan and Republican National Committee chairman Reince Priebus fail to speak up even when Trump shames himself and the GOP.

Among the Republicans who are running for president, only a few of the also-rans (South Carolina Senator Lindsey Graham and Ohio Governor John Kasich) have bothered to develop consistent or consequential critiques of the front-runner’s abusive and irresponsible behavior.

Even when Republican candidates know Trump is wrong, they often give him a pass—as New Jersey Governor Chris Christie did when he was asked about Trump’s claim that “thousands and thousands” of Muslims in northern New Jersey celebrated the September 11 attacks on nearby New York City. “I don’t recall it happening. I don’t think it did,” was the tepid initial response from the usually feisty Christie, who only later got around to pushing back against Trump’s outlandish rewrite of history.

When they should be calling Trump out, the other Republican candidates instead embrace the worst of his politics. Trump’s fantasies are facilitated by supposedly “mainstream” Republicans, who seek to advance themselves by being even more outrageous than the man who continually sets new standards for political outrageousness.

The bottom line is this: Most Republicans, be they candidates or party leaders, do not want to say “no” to Donald Trump. And their cowardice only empowers the blowhard, as it creates a new definition of what is permissible in a race for the nomination of the party of Abraham Lincoln, Teddy Roosevelt, Dwight Eisenhower, and Ronald Reagan.

But the Republicans who would be president are not the only ones who have, for the most part, failed to say “no” to Trump.

As the billionaire has made himself the king of all political media, broadcast and cable executives have tended to salivate at the prospect of Trump appearances on their networks. When cable networks promote Republican debates, Trump is featured at the front of ads that have all the subtlety of World Wrestling Entertainment promos. So, while Trump may face some questions and challenges, he is not used to hearing the word “no” from media anchors and editors and CEOs.

In fact, when Trump and Carson made pre-debate demands of CNBC—for a shorter format—the network capitulated.

So it was a big deal when CNN Worldwide President Jeff Zucker said “no” to Trump on Thursday.

Earlier in the week, the billionaire candidate threatened to boycott CNN’s December 15 Republican debate unless the news network donated $5 million to the veterans charity of Trump’s choice.

There’s nothing wrong with objecting to the way in which the networks seek to profit from what should be a public service. Debates ought to be aired without commercials, and they should be broadly available at no cost for viewing on every available media platform.

There’s certainly nothing wrong with encouraging businesses to give money to charities that serve veterans—especially if that encouragement is coupled with an absolute demand for full funding of the Veterans Health Administration and other VA programs.

Unfortunately, there is something wrong with an individual candidate threatening to skip a debate if a network does not adjust its business practices to satisfy his demands—and potentially to help him improve his public image.

Trump’s gaming of the media is troublesome enough. But what’s really unsettling—as the CNBC capitulation illustrated—is the extent to which media outlets have bent to his badgering.

So when Trump made his demand of CNN, everyone was watching for the network’s answer.

To his credit, Zucker provided that answer directly—and correctly.

Asked Thursday for his response to Trump, the CNN executive said, “No.”

“We do not pay candidates to appear,” Zucker explained at a Paley Center for Media event.

Zucker did not say “no” to covering Trump, or to covering Trump fairly. In fact, Variety reported that Zucker declared, “It’s our role to report what he says, what he does, to fact check what he says and what he does.”

How Trump will respond to Zucker’s “no” remains to be seen. There’s a good chance he will show up for the December debate—as he did for a September CNN debate. Trump had demanded in a letter to Zucker that all profits from the debate be donated to charity. The CNN head did not respond and Trump let the matter slide—until Monday.

If by chance Trump does not show on December 15, so be it.

There are some lines that have to be drawn.

And there are some words that must be spoken.

With Trump, the first of those words is “no.”

Only when political and media elites learn to use it, as Zucker did, will there be any chance that the 2016 contest could start to get serious.