“We’re not talking about the truth; we’re talking about something that seems like truth – the truth we want to exist.”

That was how comedian Stephen Colbert explained “truthiness”, the term he coined in 2005 to refer to “truth that comes from the gut, not books”.

Last year, when Oxford Dictionaries declared “post-truth” its word of the year, Colbert returned in character to denounce what he called “clearly a rip off”.

The Trump administration has embraced truthiness with gusto: think of Kellyanne Conway’s enthusiasm for “alternative facts” about the size of Trump’s inauguration crowd.

But what, though, do we make of the liberal response to Michael Wolff’s new Trump book Fire and Fury?

In a review for Fairfax, Matthew Knott acknowledges that some of Wolff’s stories are probably apocryphal and other incidents have been flatly denied by supposed participants. But then comes this:

One suspects, though, that many readers will forgive any such errors. The book confirms their worst fears about the Trump presidency: it feels truthful, if not always factual.

Does that not sound very similar to “truth from the gut”?

“Do not be distracted,” writes Matthew D’Ancona, “by those who are scouring the book for minor errors. The big story is what matters, and Wolff has nailed it.”

Yes, every text contains mistakes and generally those incidental snafus don’t matter. Yet Fire and Fury offers a fly-on-the-wall perspective on the Trump administration, with novelistic descriptions of encounters between the main players. Wolff says he conducted extensive interviews but gives no specific sourcing for the verbatim dialogue he presents.

In that context, “minor errors” in the checkable material take on considerable importance when we come to stuff we must take on trust.

Extraordinary claims require extraordinary evidence. We’re talking about a book that’s not merely unflattering about Trump but one that describes a president so intellectually feeble that we expect to read that Jared Kushner waters him daily.

For perfectly understandable reasons, much of the world despises Donald Trump. But that loathing means we should be more, not less, suspicious of claims that accord with our prejudices.

Just as excerpts from Fire and Fury began to circulate, the cartoonist Ben Ward (@pixellatedboat) tweeted what looked like an extract from the book. It described the desperate efforts of Trump’s flunkies to provide a dedicated “gorilla channel” at the White House so that the president could watch hours of the primates fighting. The passage concluded:

“On some days he’ll watch the gorilla channel for 17 hours straight,” an insider told me. “He kneels in front of the TV, with his face about four inches from the screen, and says encouraging things to the gorillas, like ‘the way you hit that other gorilla was good.’ I think he thinks the gorillas can hear him.”

The tweet duly went viral, reposted thousands of times by astonished social media users, including a remarkable number of journalists. The gorilla channel felt truthful, even if it wasn’t factual.

Remember, Colbert presented “truthiness” as a response to the bluster with which Bush and his handlers manoeuvred America into the Iraq quagmire. Back then, progressives espoused a Gradgrindish enthusiasm for the facts.

If you didn’t watch Fox News, you boasted about your membership of “the reality-based community”, in a nod to an infamous quote given to the New York Times’ Ron Suskind by a White House aide.

The weaponised duplicity of the Bush crew duly gave rise to a liberal passion for the so-called fact-checking units that proliferated briefly everywhere. In the 2013 Australian election, for instance, voters could check the candidates’ utterances via dedicated fact check units run by the ABC, the Conversation and Crikey, as well as at a local incarnation of PolitiFact.

In 2014, I suggested that the “just the facts” fad wouldn’t achieve its implicit goal of effectively adjudicating debates, since the media no longer enjoyed sufficient authority to act as a kind of political umpire. That era’s gone – and it’s not coming back any time soon.

But that doesn’t make the current outbreak of progressive truthiness any less dangerous. Over the last few weeks, we’ve seen growing chatter about how the president’s mental health warrants some kind of medical intervention – a discourse that supplements an earlier insistence that he should and would be removed as a Russian spy.

This stuff is a wish-fulfilment fantasy for progressives and an obstacle to any real movement for change.

Trump remains what he’s always been: a walking, talking embodiment of resentments and entitlements. He’s not a Russian agent, he’s a Fox News segment brought to life by decades of culture war.

It’s hard to think of anyone for whom a psychological assessment would be less useful than the current president, a man who’s all surface and no depth. With Trump, what you see is what you get.

In that context, as Slate’s Yascha Mounk says, applying the 25th amendment to remove “a president who appears to be operating much the way he has publicly done for many decades would amount to staging a judicial coup”.

And, no, a judicial coup would not be a good thing, even if it took Trump out of the picture.

It’s not simply that Mike Pence, the man who’d become president, is himself a dangerous ideologue. It’s also that undemocratic means do not bring about democratic ends. Fairly obviously, the use of psychiatric diagnosis to bring down an elected leader would set a disastrous precedent.

That Trump can be magically dethroned might be a truth that we want to exist – but that doesn’t make it true. Instead of truthy fantasies, we need to face reality.

A huge popular constituency exists for an anti-Trump campaign. All over the world, this president is loathed not just because of his personality but because of everything he represents. Rather than imagining a shortcut by which Trump might be removed, or obsessing about insider gossip, we need to mobilise ordinary people in defence of a better world – and that means a rapid change of emphasis.