Joseph Holt is an ethics professor at the University of Notre Dame's Mendoza College of Business. The views expressed here are solely the author's. View more opinion articles on CNN.

(CNN) It is a sad day for democracy when the leader of the free world repeatedly calls the press the "enemy of the people," and his chief spokeswoman can't bring herself to say that isn't so. Yet that is what happened Thursday at a White House press briefing.

CNN's Jim Acosta -- who was aggressively jeered at a Trump rally Tuesday -- asked White House Press Secretary Sarah Huckabee Sanders to acknowledge that the mainstream news media is not in fact the enemy of the people -- as Ivanka Trump had done earlier that day. Sanders not only couldn't bring herself to acknowledge that, though given multiple opportunities to do so, but defended the President's stance toward the press as "completely understandable" given his belief that the media is biased against him.

President Donald Trump ramped up his attack on Thursday night at a rally in Pennsylvania, calling members of the press " horrible, horrendous people ." That language is dangerous, and calling the press an "enemy of the people" is bizarre. A real enemy of the American people seeking to undermine our democracy would love nothing more than to shut down the press.

One of the reasons Trump's language about the press is so disturbing is that it suggests Trump would prevent mainstream media from criticizing him if he had the power to do so. That is the likely spirit in which the White House banned CNN reporter Kaitlan Collins from a White House press event last Wednesday. Collins, who like Acosta and other members of the White House press corps conducts herself with a high level of professionalism, was told she was banned for asking the "inappropriate" questions that any good reporter in her position would have asked (but that the President evidently did not want to hear).

Thomas Jefferson, writing in 1792, maintained , "No government ought to be without censors; and where the press is free, no one ever will." The press stands vigilantly as a bulwark against tyranny and the falsehoods that feed it. Truly democratic rulers would not want to live in a country without a vibrantly free press -- only a tyrant or a subject content to live under tyrannical rule would. Far from being the enemy of the people, the press at its best is like a guardian angel that caringly and capably protects us from harm.

The press is also made up of human beings, and like all of us they sometimes make mistakes. A few for the political press that come to mind include "Dewey Defeats Truman," the botched banner headline on the Chicago Daily Tribune front page after President Harry S Truman defeated Thomas Dewey in 1948; the less-than-incisive coverage by many in the run up to the Iraq War; and the erroneous predictions of a Trump defeat in 2016. Be that as it may, the role the press has played and will continue to play in being a voice for the people and a check on indiscriminate power cannot be overstated.

The label "enemy of the people" can be applied to the press only in the ironic sense in which it is applied to the protagonist of Henrik Ibsen's 1882 play of the same title, though that character is courageously trying to help the people in his hometown.

In the play , the town has launched a marketing campaign to lure visitors with mineral baths that supposedly have healing powers. The protagonist, Doctor Thomas Stockmann, discovers that the baths in fact pose a serious health threat due to contamination from upstream pollution. He wants the baths to be closed and the problem addressed. But the baths were expected to bring economic prosperity to the town, and town leaders and the mob who supports them want to keep the baths open and the money rolling in.

The press in the play sides with the powers that be against the truth, providing an example of the harm that arises when the media fails to perform its protector role responsibly. Stockmann and his family receive threats, but he sticks to his convictions. In the final act, the windows of their house are smashed. The closing words in Arthur Miller's adaptation of Ibsen's play, which debuted on Broadway in 1950, are "The strong must learn to be lonely!"

The role of Stockmann in the play is like the role of mainstream media in democratic society -- a revealer of truths that some of those in power, for their own selfish reasons, would like to keep hidden. Journalists are uniquely qualified to perform that vital role of discovering truth and combating falsehood. They have the unique skills, training and resources required; the courage and commitment needed; and an obligation under a demanding code of journalistic ethics to be responsible for the accuracy and fairness of their statements in a way that other sources of news and opinions not bound by the code -- including a President who impressively averages 7.6 mistruths a day -- are not

Follow CNN Opinion Join us on Twitter and Facebook

We thank soldiers for their service because they devote themselves to protecting our freedoms, and we should. But we should also thank the media for the same reason -- especially when the stakes have never been higher.