Pete Evans is a restaurateur famous – or notorious – for his advocacy of the “paleo diet”. Evans argues that modernity is making us sick, and that we should abandon processed foods, refined sugars, cereal grains and dairy, and assume a diet closer to that of our Palaeolithic forebears – essentially, meat and veg.

Two years ago, an Evans cookbook containing recipes for infants was pulped after health officials raised concerns. “In my view, there’s a very real possibility that a baby may die if this book goes ahead,” the president of the Public Health Association, Professor Heather Yeatman, said at the time. The same week another publisher, Penguin, cancelled their own cookbook with fraudulent “wellness” campaigner Belle Gibson.

Evans has generated controversy elsewhere, notably in his opposition to water fluoridation – a “known neurotoxin”, he told me. On Channel Seven’s Sunday Night program last week, he made similar assertions. “Why,” he asked, “are doctors experts in fluoride and what are their qualifications to be up to date with the neurotoxins that fluoride is?”

It was a pathetic performance. When asked about his medical qualifications – he has none – Evans sneered at their importance. Instead, he implied the medical industry was corrupt. “What do you need a qualification for to talk common sense?” Evans said. “Why do you have to study something that is outdated, that is industry-backed, that is biased, that is not getting the results? That would be insane to study something that you’re gonna waste your time with? That’s just crazy. It’s just crazy.”

For his supporters, that research means trawling Google to find something to support their exotic suspicions. Spend enough time, and you will.

Clinical Associate Professor Matthew Hopcraft of Melbourne University’s dental school wasn’t impressed. “Common sense would tell you that the experts, who have spent years doing the actual research, are the ones that we should be listening to, not the armchair experts like Pete,” Hopcraft told me. “We have a situation now where people who don’t understand the science try and legitimise their position by saying that their common sense trumps scientific evidence. It’s a perfect example of the Dunning–Kruger effect or cognitive bias, where, despite his lack of knowledge or understanding, Pete Evans thinks he is an expert in the health effects of water fluoridation, because he’s read a few articles online. I would hope that his commonsense approach to expert matters doesn’t also apply to things like flying a plane. He criticises health professionals who spend decades to become experts, and wants people to believe that he knows more than them ‘just because’. It’s ludicrous.”

Evans chastised his interviewer for being unprepared, but was unwilling to cite or explain the reports he vaguely invoked. There were 1.4 million viewers that night, but instead of enlightening them, he promised to privately send his interlocutor “the studies ... there’s a mountain of evidence out there”, which is of little use to the audience. It sounded a lot like the cab driver who had become expert in foreign policy via talkback radio and, when questioned, gestured helplessly to some distant cloud of corroborative literature. If there are indeed “mountains” of evidence showing that Australia’s fluoride policy is dangerous, we might have hoped that Evans would be our Sherpa.

I asked Evans for the “mountains” of evidence. He referred me to two books, The Fluoride Deception and The Case Against Fluoride. “They are great starting places for your own research, and full of science,” he told me.

The Australian Medical Association isn’t so sure. Its president, Dr Michael Gannon, characterised Evans’ arguments as flaky and irresponsible. Hopcraft agreed: “I have a couple of criticisms of Pete Evans. Firstly, he was supposed to be answering his critics, but in fact offered no defence at all. If he truly understands the science like he claims, then he would have no problems in laying out his position, and providing the evidence.

“If he wants to use his profile and platform to claim that water fluoridation is not safe and effective, then he has an obligation to actually argue his case. This is a real problem, because people are clearly influenced by what he has to say, and you can see this on social media. I think what then makes this worse is that he is building this as a big conspiracy, playing into people’s fears. And the danger is real, because we know that there is a push from a very small minority of anti-fluoridationists to pressure local councils to remove fluoride from the water supply, and this has already happened in Queensland in a number of towns. There was an anti-fluoridationist party that ran candidates in the recent Western Australian election, and Pete’s comments help to support those actions. If we start down the path of removing fluoride from the water, then we are losing a key population preventive strategy that has shown time and again to improve dental health.”

Evans also said: “Myself and other doctors and scientists believe that we should have a choice. If people wish to add fluoride into their family’s water then they can do so. Myself and others are opposed to mass medication through our water supply, using a known neurotoxin.

“This is especially [the case], as more and more people are using baby formula to feed their babies and using tap water with the fluoride in it as their water source. How much fluoride is in breast milk compared with a bottle formula that has been made using water with fluoride in it?

“My team and I consult the world’s leading scientists, professors and researchers and share that information and we should always consult our health professionals and work in conjunction with modern medicine.”

There is something of Donald Trump in Evans’ rhetoric. It’s impassioned but hazy. It turns ignorance into virtue. Says media criticism is ugly and unfair. Without evidence, Evans impugns experts as to better hoist the flag of “common sense” and validate his lack of professional qualifications.

Like Trump, Evans can depend upon a base of acolytes – and speak to them directly through social media – who reinforce his position as a brave and lonely truth-teller. This week, Evans posted to his Instagram page the cover of the latest Beast magazine, featuring his relaxed and handsome self. The image was accompanied by: “Thanks to the crew at The Beast for conducting an intelligent and honest interview (it’s been a while!)”

The implication was obvious: the Sunday Night interview was poor journalism. And it was. But not for the reasons Evans thought. The interview was a masterpiece of inanity and self-promotion, and yet its subject was still aggrieved by the 10 per cent of questions that invited him to explain his ideas. It’s a dodgy ego that can be injured by a puff piece on the TV network he stars on.

Evans’ fans thought differently. Their comments variously expressed contempt for the journalist, love for Evans, and support for Dr Andrew Wakefield, the discredited doctor who “discovered” the link between vaccination and autism. This support is incurable.

Evans can speak plainly and effectively about the importance of diet. There are many – probably thousands – who claim Evans as their inspiration for eating healthier, and feeling better. This can’t be discredited. Nor can the reasonable advice be called complicated. Evans is profitably suspicious of Elites and The Industry, but there isn’t a GP who wouldn’t tell you the same things: less booze, sugar and processed food; more exercise, vegetables and home cooking. These aren’t secrets.

Evans is right about some things. This does not make him right about everything. Having changed a life for the better does not mean he can’t change one for the worse.

To watch Evans point to marginal and discredited sources is to be introduced to a logical fallacy: that the mere existence of an argument testifies to its validity. It’s a dangerous fallacy in a time when every conceivable theory or prejudice can be found somewhere on the internet. To read a trail of comments on a Pete Evans Facebook post is to read numerous demands that detractors “do proper research”. For his supporters, that research means trawling Google to find something to support their exotic suspicions. Spend enough time, and you will.

Paranoia and conspiracy are rampant. They always have been. But only recently have these conditions had the internet to fan them. Climate science is a Marxist conspiracy. September 11 was an inside job. Vaccinations cause autism. Each suggests a vast network of insiders secretly working to hurt you. Never before have we been able to so ubiquitously share information – and never before have we been so able to absorb so much nonsense.

Belle Gibson was a dangerous charlatan, but not a talented one. Her lies were sloppy and implausible – although none of this prevented one of the world’s most prestigious publishers conferring on her story a $130,000 advance. In an internal Penguin video, where publicists assumed the role of sceptical journalists, Gibson announced that she had just been cleared of ovarian cancer – but was unsure of when she heard this news. She was equally vague on the doctors, diagnoses and recipients of her charitable donations. It was a mess. But a mess Penguin continued with until journalists started asking questions.

In a world capable of infinite spin, a world in which its most powerful man feels entirely unrestrained by truth, the trustworthiness of our institutions is paramount. Trust is often our substitute for understanding. “There is a lot of so-called research out there, but one of the challenges is to be able to decipher the good-quality and bad-quality studies,” Hopcraft says. “Understanding research methodology and statistical analysis are important in being able to understand the value of a given piece of research. One of the problems with a lack of scientific literacy is that people Google some information, read a conclusion and take that as being an absolute fact, without having the tools to be able to critically appraise the research. So we see this in the fluoride debate, where people use Google to find their information, and they read some anti-fluoridation blog posts, and think that they have ‘done their research.’ There seems to be a lot of distrust of science, and it seems to be growing. The ready availability of information online means that everyone now sees themselves as an expert in any given field, and their confirmation bias means they continue to seek out views that reinforce their own. For example, Pete Evans has more than 1.5 million followers on Facebook, but he actively deletes any negative comments and regularly blocks people who disagree with him. So his followers only ever hear one side of the story, and that’s very dangerous.”

A cliché in our language is “healthy scepticism” – a scepticism that’s supple, moderate. What Evans’ and Trump’s supporters possess is unhealthy. It’s an antisocial scepticism, a roiling, conspiratorial kind that sees folly and corruption everywhere. And I suspect it’s increasing.