Vegans like me seem to unsettle a lot of meat-eaters, particularly around the dinner table. It doesn’t even matter if we stay quiet about our chosen lifestyle; I find that carnivore friends spontaneously start justifying themselves to me, even though I didn’t ask. It’s as if their morality is challenged by the mere presence of someone who’s thought about it and decided to be vegan.

These sorts of meat-eaters have a favourite wisecrack: “Bacon, though…”

Vegans have heard it a million times. For many people, bacon is the deal-breaker. I’ve lost count of the number of times someone has said to me: “I would go vegan, but I wouldn’t be able to live without bacon.”

I wonder if people would allow the streaky snack to stand in the way of morality if they knew how intelligent and loving pigs are.

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Researchers at Cambridge University discovered that pigs are as smart as three-year-old humans. They can follow logical processes, learn sign language and play computer games.

Neuroscientists at Emory University found that pigs can solve problems as well as chimpanzees. Even a slaughterman who killed pigs for a living said: “I reckon they got more sense than we have.”

Experts say that pigs have huge emotional depth: they display trust, empathy, forgiveness, grief, fear, sorrow and joy. In one study they were observed displaying empathy for others who were happy or stressed.

Pigs can dream and sing. In the wild they like to chase each other, play-fight, and roll down hills for fun. They show loyalty, and can remember someone they met as long as three years previously.

Bacon, though.

These wonderful animals have often saved people’s lives. A pig called Priscilla rescued a mentally challenged boy who was drowning in Texas’s Lake Somerville by swimming him to safety as he held onto her collar. A pig called Lucky saved a woman and her two grandchildren by waking them as their Illinois home began to burn down.

In Pennsylvania, a pig called Lulu saved the life of her owner, who had suffered a heart attack in her trailer. Lulu scraped her way out of the home and lay down in the road, bringing traffic to a standstill. When a driver got out of his car, Lulu led him back into the home, where an ambulance was called.

What love they show us – and what wickedness we show them in return. In intensive factory farms, sows are artificially inseminated over and over. The majority of sows reared in Britain are kept in metal crates just centimetres bigger than their bodies.

Even in farms with higher welfare standards, little piglets have their ears punctured, teeth clipped and tails cut without anaesthetic. On some farms, piglets who grow too slowly are killed by being slammed headfirst onto concrete floors. This standard industry practice is called “thumping”.

Around 86 per cent of pigs slaughtered for food in the UK are killed in gas chambers. Yes, gas chambers. As Jane Dalton’s recent long read for The Independent revealed, pigs “scream in pain and gasp for breath while the gas acidifies their eyes, nostrils, mouths and lungs,” and “scramble to try to escape, panicking and in distress” before they “literally burn from the inside out”.

Bacon, though.

The human race’s complex relationship with pigs was shown in 1998, when two pigs escaped from an abattoir in Wiltshire, swam a river and ran off.

The pigs – Butch and her brother Sundance – spent a week on the run. They were dubbed the Tamworth Two and became a media sensation. Over 100 journalists drove to the south-west to search for them in muddy woods. Television crews hovered above in helicopters.

The pigs were mentioned in parliament and on Radio 4’s Thought for the Day. When their owner said that once they were found he would take them back to the slaughterhouse, there was a public outcry. These national heroes were eventually rehomed at a sanctuary. Sundance lived to be 14 years old.

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The saga captured what scientists call cognitive dissonance. Most of the people cheering on the Tamworth Two were meat eaters. The same people tucked into pork chops or bacon sandwiches straight afterwards. But the thought of those two pigs getting killed still upset them.

It’s the same with pigs in popular culture. Peppa Pig and the piggy star of the movie Babe capture the hearts of all who watch. But what sort of love is it? Most of the same kids who are captivated by Peppa and her friends are also fed the flesh of other pigs – pigs that have had a hellish life and terrifying death. What would Peppa say?