What is the cardinal of Cologne's secret gripe?

He's bonkers to criticise his new stained glass window for Islamic overtones - there must be something else going on.

Gerhard Richter has used small squares to create a modern, pixellated effect. Photograph: Hermann Knippertz/AP

The sacred precincts of Cologne cathedral have this month become the setting for an unholy row about modern art.

The city's Catholic archbishop, Cardinal Joachim Meisner, is complaining about a stained-glass window created by the artist Gerhard Richter. The window, in the south transept of the building, is made up of roughly 11,200 coloured squares, creating a pixelated effect. It's an appropriate monument for the computer age and many locals have welcomed the return of a bit of colour to this part of the cathedral. Since the second world war the gothic tracery had been filled with plain glass.

Not everone is happy, though. Richter, an elder statesman of the German art scene whose paintings sell for millions, was probably thought of as a safe pair of hands for the job. Choosing an abstract design must have seemed like a sure way to avoid controversy but, quite unexpectedly, comments from the cardinal have stirred interfaith tensions. He has said that the window's lack of human figures is a nod to Islamic art and that it would be more suitable for a mosque than a church.

This is, frankly, bonkers. First off, gothic, the style most closely associated with ecclesiastical buildings in northern Europe, is an essentially abstract form. Sure, there's always room for sculptures of saints and kings in their niches, but fundamentally it's as non-representational as any Islamic mode of design. The famous 16th century rose window at York is a magnificent example of abstract glasswork that the cardinal would do well to cast his eye over.

Second, there was really no need to talk about Islam at all. True, it discourages the portrayal of humans or other living beings in its religious art, but there's a rich tradition of figures in secular Persian ceramics. And it's really not unusual to see the rules bent in some religious contexts too, as this manuscript from Afghanistan shows. For many Christian denominations indeed, art involving human figures is at least as strictly prohibited, if not more so - the puritans were Christians, after all. So why did the cardinal need to drag Islam into the debate?

I suspect it's something to do with plans to build a huge new mosque in the city. Cologne has a population of 120,000 mainly Turkish Muslims, but the current mosque caters for only about 600 worshippers. Designs for a new one, in the Ottoman style, have brought far-right groups out on the streets to protest.

So is the cardinal actually worried that his cathedral might soon be overshadowed by minarets? If that's the real reason for his outburst, there's no reason to take it out on poor old Gerhard Richter. Or, for that matter, Islamic art.