I have said since Donald Trump got into the campaign that he has every right to hit back at the media that he believes covers him unfairly.

I have said after each controversial story and each attack that while the president's language is occasionally too harsh, the relentlessly negative coverage is fair game for his counterpunching approach.

But the president crossed a line yesterday that he should not have crossed in calling for the heads of two major networks to be fired.

I knew when I said that on Fox that I would be strongly criticized by some Trump supporters. But I have to be consistent.

A president of the United States using his bully pulpit to demand the firing of corporate executives, simply because he doesn't like their media coverage of him, is unprecedented and troubling.

And if President Obama had urged Fox News to fire Roger Ailes, there would have been an explosion on the right.

At the same time, CNN in particular has given him a big target with a flawed story that it refuses to clarify or correct. The story said Michael Cohen is ready to tell prosecutors that the president knew in advance of the Trump Tower meeting with a Russian lawyer. Cohen’s attorney Lanny Davis, who tells me he did not confirm the allegation when he spoke to CNN off the record, calls the account false.

Trump has a special resentment toward Zucker because they worked together during his "Apprentice" days, when Zucker ran NBC.

The president took to Twitter to accuse CNN of "hatred and extreme bias" against him, and then slammed CNN President Jeff Zucker by addressing the network's new parent company:

"Little Jeff Z has done a terrible job, his ratings suck, and AT&T should fire him to save credibility!"

That was after CNN hit back at an earlier Trump slam saying: "Make no mistake, Mr. President, CNN does not lie. We report the news. And we report when people in power tell lies. CNN stands by our reporting and our reporters."

One of those reporters, on the hotly disputed Michael Cohen story, is Jim Sciutto, a political appointee in the Obama administration. Another is Carl Bernstein, the onetime Watergate sleuth, who has continually hammered Trump as a CNN commentator.

Bernstein has called Trump an "authoritarian," said his tenure is "worse than Watergate," and that "this is the greatest journalistic challenge of the modern era, to report on a malignant presidency.”

I know Carl and I respect him, but those are not the words of an unbiased reporter when it comes to Trump.

During the tweetstorm, Trump called Bernstein "sloppy" and "a man who lives in the past and thinks like a degenerate fool, making up story after story."

Bernstein responded that "I have spent my life as a journalist bringing the truth to light, through administrations of both parties. No taunt will diminish my commitment to that mission."

The president also went hard after Andy Lack, the NBC News chairman.

"The good news is that Andy Lack(y) is about to be fired(?) for incompetence, and much worse," he tweeted. That is purely an unsubstantiated rumor. NBC has made no comment.

And then there was this about NBC: "When Lester Holt got caught fudging my tape on Russia, they were hurt badly."

There is no credible allegation that the NBC anchor engaged in misleading editing of his interview with Trump last year. That was two days after the firing of Jim Comey, when Trump stunned the world by saying he canned the FBI director "regardless of recommendation" and brought up the Russia investigation. NBC posted the entire 13-minute interview online.

Again, there is no shortage of shoddy, hyped or inaccurate journalism for President Trump to challenge. He doesn't help his case when he makes unfounded charges or uses his megaphone to say that media executives should be fired because he doesn't like their companies' coverage.