Last weekend, the world woke to find Morrisons had projected an image of a cut-price baguette on to the outstretched wings of Antony Gormley's iconic public artwork The Angel of the North. The stick of bread was the perfect shape to occupy the Angel's wingspan, and one wonders what other products Morrisons might have filled Gormley's emotionally resonant secular sacred space with next. A toilet brush perhaps? Or maybe a vibrating anal probe? Except that Morrisons don't sell vibrating anal probes. They have standards.

Illustration by David Foldvari

Critics suggested a boycott of Morrisons. I suggest we continue to shop there, but always take a large Party Egg off the shelf and eat it, whole and unpaid for, before reaching the checkout. This is what I do at Sainsbury's on Green Lanes every week, as the hypocritical arts-patronising chain withdrew a DVD of mine from sale after protests from the religious right in 2005. At this rate, Sainsbury's will soon be bankrupt and I will be 18 stone of ersatz sausage meat.

Back in 1998, when he was first installed near the A1, all the Geordies hated the Angel. They ran around naked in Big Market, licking pease pudding off each other's hands, and bellowing the usual arguments about how many kids' football pitches the sculpture could have paid for. In the war against art and thought sport always seems to be the trump card. But can I be the only person who looks at the £8.92bn price tag of the London Olympics and thinks: "That could have paid for 1.8bn different 50-seater fringe theatre productions, each with the potential to change lives for ever, and none of them requiring the presence of Boris Johnson and the Dow Chemical Company?"

In the end Gormley won the battle for hearts and minds. His 2003 piece at Newcastle's Baltic, Domain Field, invited hundreds of sceptical locals to be caked in wet plaster and made into a massive piece of Art. Geordies love getting plastered, and suddenly the people took proud ownership of their Angel. It's fair to say Morrisons picked the wrong quasi-religious industrially themed icon to project a cut-price loaf on to. But the supermarket's action was not without precedent.

I do not believe in God, but the image of the Angel of the North moves me, as do the relics of our distant spiritual heritage strewn randomly around the British landscape: Stonehenge, the Cerne Abbas Giant, Ann Widdecombe, and the former archbishop of Canterbury, Rowan Williams. In March 2012, the stupid bookmakers Paddy Power celebrated the Cheltenham horse murdering festival by drawing a jockey overnight on to the 3,000-year-old chalky flanks of White Horse of Uffington. Paddy Power claim to have done no damage and instead their own blog invited us to think of them as "lovable scamps" and "mischief makers", the Horrid Henrys of wilful cultural vandalism.

Presumably the bronze age visionary Thongor of the Chalky Horse That Looks A Bit Like A Duck still sits, resigned to fixed fate, in whatever pre-Christian netherworld he now calls home and, like Gormley, concedes: "I'd rather the work was not used for commercial purposes, but it's out there now," unable and unwilling to deal with copyright matters connected to the appropriation of his Picasso-anticipating dream of equine energy to promoting betting shops and gambling debts.

It was early Sunday morning when I read about Morrisons. I had awoken in a bespoke yurt, in the green fields of the Machynlleth comedy festival, in the shadows of Snowdonia, and my annoyance with the heartbreaking illuminated baguette was doubtless sharpened by a weekend spent at this peerless boutique event, where culture never comes second to commerce. But I am a puritan relic of an age undreamed of, when the Clash wouldn't do Top of the Pops, even Mötley Crüe wouldn't play South Africa, and when, if John Peel did do advert voiceovers, he at least sounded slightly ashamed.

But those days are gone. Our last culture minister suggested that public art's only value was commercial, and our new culture minister supports ticket touts, suggesting culture's value is merely whatever the market wants to pay for it. In receipt of such mixed messages, is it any wonder Morrisons looked at the aching wingspan of Gormley's Angel and saw only an empty space that wasn't being maximally monetised?

And that's where we are now. Ancient forests can be destroyed, if equal amounts of trees are planted somewhere else, an inherent sense of place and historical resonance translated into the worth of its mere weight in wood. It's me that's out of step, I am sure. If we can advertise on ancient hill figures, and publicise on public art, I wondered, as I drove home across Wales, what other monetisable spaces, previously considered sacred, are we failing to optimise? And then it struck me. The subconscious itself is going to waste. What of those unmanageable moments, where we are struck by beauty and meaning we had not foreseen? They are what makes us human, admittedly, but is there some way to make them pay?

Aiming to cross the Severn by the M4, I stopped at Tintern Abbey, and dragged our sleeping children into the sunlight. Normally I would have pointed them at the romantic ruin and lectured them on how it inspired in Wordsworth, Turner and Tennyson the apprehension of the sublime. Instead, I forcibly marched them around the site, chanting: "Buy Morrisons bread! Gamble at Paddy Power! Buy Morrisons bread! Gamble at Paddy Power!" until, crying and ashamed, they begged me to stop.

Dovetailing through Caerleon, where the Welsh mystic Arthur Machen saw the Great God Pan, I wandered the woodland glades shouting at walkers, "Buy Morrisons bread! Gamble at Paddy Power! Buy Morrisons bread! Gamble at Paddy Power!" and then, somewhat distressed, I vomited in the churchyard of St Cadoc's, the residue forming the perfect outline of a Morrisons baguette upon an ancient grave.

We drove on, to the Aust service station on the M4, where, just short of the Severn Bridge, a Vauxhall Cavalier, belonging to Richey Edwards from the Manic Street Preachers, was found abandoned in February 1995. In the Costa Coffee I carved into my arm with a razor blade the words "Buy Morrisons bread! Gamble at Paddy Power!" Now no one could doubt my sincerity, my fitness for purpose in this brave new age. My arm hurts. My children are embarrassed. There is sick everywhere. And blood. Who do I invoice? There must be some way of getting all this thoughts and feelings shit to pay for itself? Come on!