Mark D. Weinberg is a communications consultant and the author of "Movie Nights With the Reagans" (Simon & Schuster). He was special assistant to the president and assistant press secretary in Ronald Reagan's White House and director of public affairs in Reagan's office. The opinions expressed in this commentary are his own. View more opinion articles on CNN.

(CNN) In a rare display of bipartisan unity, Republican and Democratic senators and representatives are practically tripping over each other to get in front of television cameras to blast Russian President Vladimir Putin for attempting to undermine our democracy by seeking to tamper with the 2016 presidential campaign. They correctly claim that interference with our elections strikes at the heart of America, is something that cannot be ignored and must not be allowed to happen again.

Mark D. Weinberg

But many of those same posturing and pontificating politicians are far too accepting of another, arguably equally grave threat to our democracy -- the demonization of a free press by President Donald Trump. By calling the press "the enemy of the people," Trump seeks to destroy one of the very pillars on which our democracy was founded and continues to stand. Freedom of the press is enshrined in the First Amendment to our Constitution because the Founding Fathers knew a democracy cannot exist without it.

It's fine for Trump to criticize the press and even call out reporters for stories that he views as unfair. All presidents have done that. I was a spokesman for Ronald Reagan for more than a decade, and it was not uncommon for him to express his dislike of a story. When he did, however, he never made it personal about the reporter, never questioned their motives, never spoke ill of an entire newsgathering organization -- let alone the entire profession -- and was almost always convinced that "they just don't understand."

Trump is free to dislike the press en masse (save a certain network that usually acts more like a squad of cheerleaders than probing journalists), though life would probably be easier for him and his staff if there were some sort of détente with the Fourth Estate.

We all know why Trump attacks the press as he does. He wants its credibility to be so broken that whenever it reports negative stories about him it will not be believed. That has ominous implications. If the President succeeds in his effort to discredit the press, then from whom will the people get the truth? The government? History is filled with examples of how disastrous that has been. Ask the people in Pyongyang, Moscow, Beijing, Damascus or Tehran how that is working out for them.

Read More