Like Christmas decorations, as we get into December, down from the attic come the grunters and moaners, hypocrites, dogmatists and self-righteous sinners. It's the season of ill will and miserableness. The usual suspects – schools, local authorities, Muslims, Hindus, Sikhs – are rounded up, charged with plotting to kill Christmas, or lethally wounding the celebrations with something called PC. PC GONE MAD!!!, to be exact.

On a popular daytime TV show I was asked what I thought of Dundee council, which decided to have blasphemous "winter lights" this year because, say their accusers, they were too scared of offending other religions. Bin Laden must be hiding in Dundee and beheadings would have followed if stars and angels had garlanded the streets. The Lord Provost of the city fought back and reinstated "Xmas lights". The audience roared with approval when the presenter laid the blame on PC GONE MAD!!!

What if, I asked, there was only good intent behind the winter lights? November and December herald joyous festivals for many communities – why not share them with each other as people of these isles? Can't we even do that? These protests are not raised at all when "Christmas" lights are bought up by big business to advertise their goods – Disney in Regents Street, for example. Ho! Ho! Ho! and a bottle of Coke.

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Next fight. Nativity plays, say sections of the press, are now being banished from schools eager to suck up to us ethnics with Diwali dress-ups and Eid delights. My children loved the story of Mary and the babe though they were always only goats and sheep. How many schools? Which ones? Where? Can we have a league table please, Ed Balls?

There is a real, nameless anxiety beneath these absurd and disagreeable national spats. The meaning of this foundational and affirming festival seems to be crumbling away, a precious edifice falling to ruin like so many lonely churches. But who did this? Who neglected to care and keep up the true spirit of Christmas and Easter? Not the so-damned army of PC enforcers but Christians themselves. They who did not halt the Un-Christianing of Britain. (Let us call it UC.)

Ralph Waldo Emerson asked in his essay on self-reliance: "Every Stoic was a Stoic; but in Christendom where is the Christian?" By throwing themselves into displacement activity, church leaders can avoid responsibility for the faith drain. Two Anglican Bishops, one of them Rev Jonathan Gledhill of Lichfield, urged Christians to wear crosses, not to show commitment but to become martyrs against PC GONE MAD!!!

Our fine-robed obfuscator, the Archbishop of Canterbury, a decent man and deep scholar, complained at the weekend that the political classes sidelined Christians and Christianity and were "focusing intently on Muslims". He chooses to ignore the crusading high church ex-PM and his worshipful Cabinet. The whine about Muslims makes the grave man sound like a complaining, selfish child whose toy is not as big as the one given to the boy next door.

Meanwhile values that determine Christian belief and behaviour – generosity, love, forgiveness, modesty, fidelity, simplicity, spirituality – fall away. Covetousness, adultery, vengeance, greed and consumerism spread through the land. Forgive me for sounding like a fire and brimstone preacher. The boy born under the star, son of God for Christians, was a lean ascetic who exhorted his flocks to sell what they owned to give to the poor.

St Nicholas, the original Father Christmas, born into a wealthy Christian family, did just that until his fortune was all gone. Somehow he mutated into the obese bringer of excess and surfeit – gluttony personified. The fat man won, pushed aside the saviour and the saint. Archbishop Rowan Williams does not boldly call out against our capitalist dystopia. And he should.

Rev Gledhill warns us, especially non-Christian Britons: "Christians aren't going to disappear quietly from the marketplace". The marketplace, he will be glad to hear, is teeming – flush with credit cards and shoppers buying drinks, party canapé trays, frocks and shoes, pure silver napkin claspers for the discerning lobster eater, snakeskin shoes, giant TVs and diamond bracelets. The churches are empty and cold. The people do not go in. Too busy or not sure what the religion stands for.

Most powerful Christians do not fight robustly enough for progressive values. There is fudge or surrender to conservatism on feminism and gay rights, for example. They could have – but didn't – deafeningly condemned Blair's war and told him not to wrap himself in their faith. A whimper here and there is all we got from the church Establishment. (The exception is Archbishop Sentamu of York.) And so it is with the lost and disenfranchised.

Many humble Christian leaders do understand their role and the crisis. They live by the eternal tenets of their faith, applying them to modern life and its myriad challenges. Take one example. Doctors from several of the Royal Colleges have called for incarcerated asylum children to be released this Christmas, as have dozens of children's authors. And so Rev. Canon James Rosenthal and Rev. Professor Nicholas Sagovsky took presents to the asylum children held in Yarl's Wood detention centre. The guards wouldn't let the kind men through.

Many of the young there are severely traumatised; some self-harm and may never recover. Mary had to seek refuge. Here, today, she would have had to nurse her infant behind razor wire and kept in her place by hardened guards. How heartening it would be if Rowan Williams, instead of moaning about the status of Christianity, had chosen instead to seriously take on the government at this time, animating the central motif of his great religion.

I have often said that some Muslims and our leaders are betraying the Islam I grew up with – their brutal Islamism steps on the faith in our hearts. Christianity too is being failed by its own and needs to rediscover its beatific roots. Love Divine is what makes this religion great and good. I don't see a vast amount of that as Christmas approaches.

y.alibhai-brown@independent.co.uk