Shooting the messenger, metaphorically speaking, is a long-established practice among American presidents and prickly politicians the world over. But by repeatedly insisting journalists should be treated as “the enemy of the people”, Donald Trump has hit a new low – with dangerous international ramifications.

From the start of his presidential odyssey, Trump made media purveyors of “fake news” a primary target. His attacks played well with partisan crowds encouraged to believe journalists were bag-carriers for the “liberal” establishment elite which, he said, was betraying the American dream.

Insecure Trump craves adulation and unquestioning praise. So as critical, intrusive reporting intensified following his election victory, so too did his personal vendettas with media organisations. Those most frequently singled out are among the most respected: the New York Times, the Washington Post, CNN.

In a tense exchange on Thursday, Jim Acosta, CNN’s much-abused White House correspondent, finally kicked back. He challenged Sarah Huckabee Sanders, Trump’s press secretary, at one of her increasingly rare briefings, to withdraw the “enemy” slur. Sanders declined, complaining instead of her shabby treatment by the press.

Acosta upped the ante: “This democracy, this country, all the people around the world watching what you are saying, Sarah... the president of the United States should not refer to us as the enemy of the people,” he said. “All I’m asking you to do, Sarah, is to acknowledge that right now and right here.” Sanders ungraciously refused, again.

Trump purposefully aggravated matters that evening at a rally in Pennsylvania, mocking the reporters present. “They can make anything bad because they are the fake, fake disgusting news,” he shouted. His ostensibly triumphal meetings with the Queen, Russia’s Vladimir Putin and North Korea’s Kim Jong-un had been reported negatively, he claimed.

The White House press corps, senior correspondents, can be a bit pompous and self-regarding. (I know. I was a member of it in the 1990s.) But it is, on the whole, a highly professional body. They take their work seriously and mostly do it impartially and well.

Despite his endless whingeing, Trump is not subjected to a higher level of scrutiny, or held to a higher standard, than previous presidents. The big difference now is that his definition of “fake news” has expanded to include any news he does not like. The commander-in-chief wants to be editor-in-chief.

Why? Maybe because he’s a control freak who cannot stand being questioned. Or maybe because he is feeling the heat from the FBI investigation into alleged collusion with Russia – and possible new allegations about past Trump Organisation money laundering.

Trump describes the Mueller inquiry as a witch-hunt fed by a hostile media. Such language carries distinct echoes of paranoid Richard Nixon, who had much to hide. White House insiders say the president’s private obsession is impeachment.

Yet Trump’s behaviour suggests a more fundamental lack of understanding of the role of a free press in a free society. Sanders said last week the president supported press freedom. “We also support freedom of speech. And we think that those things go hand in hand,” she said.

The proliferation of rightwing websites, “shock jock” radio talkshow hosts in the tradition of Rush Limbaugh, and TV networks such as Fox News that make little or no pretence at objectivity or impartiality, and which ruthlessly lambast opponents, is justified by the same freedom of speech argument – even though the speech in question is often hate-filled and mendacious.

Alex Jones of Infowars, who has falsely claimed that the Sandy Hook murders were faked. Photograph: Lucas Jackson/Reuters

A prime example cropped up last week when the parents of children murdered at Sandy Hook elementary school in Connecticut in 2012 sued Alex Jones, the far-right founder of the Texas-based Infowars website who claimed, falsely, that the government staged the massacre to justify tougher gun controls.

Trump is adept at recycling favourable coverage from tame media outlets to further boost his agenda. Thus the hard-right Breitbart website recently regurgitated his comments lauding “celebrity” commentators who back his threat to shut down the federal government before November’s elections – thereby forcing a showdown with the Democrats. “You know who thinks it should be [shut down] before?” Trump asked. “Rush Limbaugh says it should be before the election, Sean Hannity [of Fox News], a lot of them. Great people.” How did it happen that a US president needs endorsement by hacks?

Trump’s divide-and-drool approach is contagious. The UK is breeding its own cohorts of rightwing, multimedia rabble-rousers aiming to upturn “political correctness” (meaning anything they don’t like) – regardless of facts, or considerations of accuracy, fairness and balance. Katie Hopkins springs to mind.

But it’s worse than that. Trump’s loathing for honest scrutiny has lethal implications. Staff at the Capital Gazette in Maryland, paid with their lives in June when a gunman decided he did not like what they wrote. Truth is not the only casualty in Trump’s media wars.

The knock-on threat is considerable. Regimes like that in Russia, where inquisitive journalists die suddenly, or in Turkey, where they are jailed in large numbers, look at Trump’s reckless shenanigans and see a green light for repression. His unpresidential message to independent voices everywhere: “Shut it or else.”