Within spitting distance of the very spot Jesus Christ was born is one of the world's great monstrosities, "a symbol of everything wrong with the human heart" as the Archbishop of Canterbury described it when he saw it for himself. And you have to see for yourself the Israeli separation wall to understand it: I don't just mean the structure itself – 30 feet high, bristling with watchtowers and formed of grey concrete slabs – but where it is built, deep into the town itself, far into the West Bank, severing Bethlehem from Jerusalem and ensuring the relentless expansion eastwards of Jewish-only settlements built on land seized from Palestinian farmers.

Getting rid of it for Christmas would be the greatest possible act of justice – not just for Palestinians, but for the Israelis, whom it deeply corrupts.

Walls don't just divide: they corrupt the soul, allowing myths to suppurate. One is that Christians are being "driven out" by Islamic extremism. What nonsense. They have coexisted peacefully with Muslims for centuries, and the Hamas government has done nothing to disenfranchise the Palestinian Christian population.

Bethlehem is shuttered and depressed not because of Koran-wielding thugs but because the wall has smashed its economy. The town has become a ghetto, severed from lands to the north and west by the wall, and to the south and east by settler-only roads and a forest of checkpoints, leaving it barely able to trade. Hundreds of acres of land has been confiscated from Christian Arabs in the name of security; Jerusalem, Bethlehem's lifeline, a mere 20-minute drive away, is now barred to West Bank Arabs; unemployment in Bethlehem is above 50 percent. That strangulation, and that alone, is the reason why Christians make up just a third of the district's population. The wonder is that so many stay.

But they do, because they are one of the world's oldest Christian populations, and this is their land. The corralled Bethlehemites see, every day, what is happening: see the high-rise white blocks which the Israelis are furiously building on land seized from their families, watch as settlers in Gilo and Har Homa hose down their cars and fill their swimming pools while they are forced to buy water weekly from trucks to fill rooftop tanks because the Israelis have diverted the water supply. They watch, they wait, they burn with anger and frustration, and are helpless to understand why the world has abandoned them.

Last week Christian leaders in Bethlehem came together to sign a "Kairos" document that names the degrading horrors of occupation: the wall, it said, "has turned our towns and villages into prisons, separating them from one another, making them dispersed and divided cantons". But the document was almost entirely ignored, not least by Christians. Their consciences will carry the burden of their abandonment of the town of Christ's birth; but I doubt those American evangelicals who believe that the land must be cleared of Arabs to make way for the Second Coming will hear these eminent Christians telling them that they have turned the Good News of the Gospel into "'a harbinger of death' for us". The destruction of the town of their Saviour's birth is unlikely to disturb their Christmas joy.

But it should disturb ours. God send His only Son into this world, into this place, at that spot – a spot now under the shadows of a monstrous injustice. We shan't get rid of the wall this Christmas. But when the Light comes into the world, some of it needs to be shed in the place where it comes; and when we let it, finally the wall will fall, and what it blankets from the world will at last be revealed. Happy Christmas.