The photograph of a four-year-old boy asleep on the floor of Leeds General Infirmary because of a lack of beds has become a fixture of this final week of the general election: not just as an illustration of the damage almost 10 years of Tory rule have done to the NHS, but because of the prime minister’s cartoonishly callous reaction to it.

The photo is horribly, brutally real. Dr Yvette Oade, the chief medical officer at Leeds Teaching Hospitals NHS trust, personally apologised for how the boy and his family were treated. But this did not prevent a conspiracy theory from emerging.

Across social media, a paragraph of identical text was shared, by multiple users often purporting to be the original, suggesting that the boy in the picture was planted there by his Labour activist mother, precisely to discredit the Tories on the NHS. The text was originally shared on the Facebook page of a woman who works as a medical secretary, who claimed afterwards that her account had been “hacked”.

The post was given considerable amplification by Conservative candidates, former MPs, a former England cricket captain, Kevin Pietersen, as well as the Telegraph columnist Allison Pearson, who quoted the text almost as if it had been sent to her by a source.

This kind of conspiratorial thinking has become all too familiar in recent years: the Leeds case almost directly parallels what happened when Boris Johnson visited Whipps Cross hospital in London earlier this year, and was berated by the father of a sick newborn who was later accused of being a plant.

But there is a tendency to discuss this sort of conspiratorialism – note this very useful Twitter thread on photo-gate – primarily in terms of disinformation or “fake news”, as if what matters most about it is that people are being factually misinformed. “Facts” and “truth” are being insufficiently defended: bad information is being allowed to push out good.

But there’s a deeper and more troubling question that doesn’t get asked as often: why do people find misinformation like this convincing – and feel driven to share it or comment approvingly in reply to it?

Our receptivity to information is shaped, in part, by the sort of evidence or testimony we have found to be reliable in the past. But it is also shaped by our desires – how we want the world to be. To cite a non-political example: if a random child produced some scribbles that resembled a brilliant work of abstract art, I would probably think this was more likely to be a coincidence than evidence of a prodigious gift. But if my own son did it, I might find myself headed to Sotheby’s and expecting it to sell for millions. When I see people sharing something like the Leeds hospital photo conspiracy – people saying that this is all a mendacious Labour plot to make the NHS seem like it’s in crisis – I feel their raging, obvious desire to believe that it is true.

There is something epistemically basic about suffering – at one point in his Philosophical Investigations, the philosopher Ludwig Wittgenstein asks us to “Just try – in a real case – to doubt someone else’s fear or pain!” His point being: it’s impossible to do honestly. If you saw someone screaming in anguish, you wouldn’t stop to ask if they were really in pain before trying to help.

Over the past nine years, the Tories have helped create a world where the relevant ethical considerations are just that basic: NHS cuts are forcing sick young children to sleep in hospital corridors on piles of coats; austerity has been linked to more than 130,000 preventable deaths. The governing party has simply introduced more suffering into the world than was in it before.

The visible presence of suffering helps indicate that things ought to be different. If you are an in any way decent person you cannot justify taking any sort of action that you know might help the Tories remain in government.

But this is a troubling thought, for all sorts of reasons. Some people want to vote for the Tories anyway, for instance because they think it will help deliver Brexit. (Although, I mean: come on. Even if you support Brexit, the Tories have had three years to deliver it. They’re playing you.) Some people feel like they’re doing all right as things stand, and don’t want to have to pay a few more pounds a month in tax. Some people, I guess, just can’t be bothered: they do not want to be saddled with the burden of caring for others.

Hence the conspiracy. Conspiratorial thinking helps people blind themselves to any and all evidence; it can be used to explain away suffering, so that people can feel like they don’t bear any responsibility to help deal with it. It deploys a seductive scepticism: what if all the evidence of our senses is wrong? What if all the poverty and strangling disinvestment anyone in the country must see signs of every day is a hoax, invented by the Labour party to help it turn the UK into a colder version of Venezuela?

What if the effects of climate change are being exaggerated, and really it’s just been a randomly hot and wildfirey past few summers? What if every homeless person you see begging, desperate and cold on the street is just tricking you – what if they take all the pennies that saps like you give them and spend them on champagne and caviar in the Little Waitrose under their £500,000 new-build flat? Why: then you might not need to care about anything beyond your own nose at all.

The people spreading the Leeds hospital photo conspiracy don’t just need to face facts: they need to face morality as well.

• Tom Whyman is an academic philosopher and a writer