Roger Ailes, the ogre-like head of Fox News who resigned following allegations of sexual harassment, had a favourite saying: “If you want a career in television, first run for president.” His friend Donald Trump took his advice. Trump, reportedly, did not expect to win the presidency in 2016. His preferred post-election plan was to launch his own TV network, with himself as the star turn.

It would have been a better outcome. From the moment he entered the Oval Office, Trump has produced daily proof of his unfitness for the job. He evidently dislikes the hard work, duties and responsibilities it entails. He spends more time away from the White House, at his private resorts and golf courses, than any recent predecessor. And despite potential conflicts of interest, he continues to oversee his business empire.

Trump is the first reality TV show president. He struggles with facts, truth and real-world choices. He has no discernible moral principles. His instincts, which govern his decisions, are mostly all wrong. His political views tend towards the ignorant, racist, white nationalist far right. The ever-sober New York Times has declared America’s president an “autocrat”. That’s quite something.

'Most excruciating of all the week’s enormities, was Trump’s disgraceful ambush of the grieving parents of British teenager, Harry Dunn.'

Trump is happier on a stage, playing to a crowd – and making it up as he goes along. He was at it again last week in Texas, reliving his greatest campaign hits in front of 20,000 fans wearing “Make America Great Again” hats. He recycled some old Hillary Clinton jokes and attacked critics who say he is not presidential enough. “It’s much easier being presidential,” he scoffed. “All you have to do is act like a stiff!”

It’s not funny. It’s alarming. A sense of dignity, along with good judgment, honesty and basic human awareness, is what is lacking in this half-real, half-fake impresario president. These gaping deficits were painfully apparent over the past week as disaster was heaped upon disaster and only Trump appeared oblivious to what Steve Bannon, his disgraced adviser, once presciently termed “American carnage”.

‘His schoolboy letter urging Recep Tayyip Erdoğan, Turkey’s president, to back down, full of threats and indiscretions, is damning proof of lethal incompetence.’ Photograph: Jim Bourg/Reuters

Look at the bodies strewn across the dusty plains of north-east Syria following Turkey’s invasion. Trump did that. Lying through his teeth, he said he did not give a green light. Now he is claiming credit for a ceasefire that rewards aggression. His schoolboy letter urging Recep Tayyip Erdoğan, Turkey’s president, to back down, full of threats and indiscretions, is damning proof of lethal incompetence.

If that seems harsh, look at the verdict of America’s fighting men. Gen James Mattis, a former defence secretary, was joined by Adm William McRaven, a former special forces commander, Adm James Stavridis, a former Nato chief, and others in condemning the Syria withdrawal as a “geopolitical mistake of near epic proportions”. Mitch McConnell, the Senate Republican leader, said Trump had caused a “strategic nightmare”. Or look at the latest testimony in Congress’s impeachment inquiry. Mick Mulvaney, Trump’s Oval Office gatekeeper, inadvertently confirmed the president used US financial aid to Ukraine to dig up dirt on his Democrat rival, Joe Biden. He later said he didn’t say what he said. He must have learned that wacky routine from his boss. It won’t wash.

Most excruciating of all the week’s enormities, in purely human terms, was Trump’s disgraceful ambush of the grieving parents of British teenager Harry Dunn. The US authorities, including the US embassy in London, acted improperly, and perhaps illegally, in facilitating the return to the US of an American, Anne Sacoolas, who allegedly drove the car that killed Dunn. Trump’s shmaltzy, made-for-TV attempt to force a surprise, face-to-face reconciliation was sickening.

Trump’s dangerous, dishonest and undignified behaviour, in these and many other instances, demeans his office. He should quit before he is impeached – and go back to being a TV host. At least he’s good at that.

• This article was amended on 21 October 2019 to correct the rank of William McRaven – admiral, not general.