Let's start with a confession: I'm not really interested in religion. If Joseph Ratzinger wants to pop over to Britain, that's fine with me, as long as I don't have to pay towards it. The Vatican can surely afford the security costs when its chief executive travels abroad to promote the brand. He is welcome to style himself Pope Benedict XVI, but I don't recognise him as a head of state, and my opinion of his morals is barely printable in a family newspaper.
That's my dilemma, in a nutshell. I'd be happy never to write another word about Christianity, Islam or any other supernatural belief system if their leaders didn't keep telling me that their ethics are better than mine. On Thursday, Mr Ratzinger had barely got off the plane in Edinburgh before he was urging Britain to resist "aggressive forms of secularism". With excitable exceptions such as Richard Dawkins, most secularists I know are pretty laid back, although we do get irritated by discrimination against women and gay people. I think that's what Mr Ratzinger meant when he urged us to respect "traditional values", and I'm glad to have played a part in the struggle to eject them from public life.
The Vatican is proud of its prejudices. It can't find a single woman worthy of becoming a priest, and it has lobbied for exemptions from UK employment law and the rules governing adoption agencies so that it can go on discriminating against gay people. It gives every impression of longing for a return to the days when unmarried girls who got pregnant were treated as pariahs, their babies taken away and their families consumed with shame. In Ireland, thousands of them were imprisoned in the Magdalene laundries run by Catholic nuns, where conditions amounted to slavery.
Now the Vatican has been engulfed by a scandal involving child-rape on a vast scale, and its response has revealed a degree of moral bankruptcy that's astounded even its harshest critics. Mr Ratzinger is the head of a church which has shielded rapists from the secular authorities.
Take the astonishing case of the former Bishop of Bruges, Roger Vangheluwe. Only last week, the Vatican announced that Mr Ratzinger would not for now be disciplining Vangheluwe, who fled to a monastery in April after admitting to the sexual abuse of his nephew. A commission set up to investigate sex abuse in the Belgian church has dealt with 475 complaints, leading to an admission that children have been abused in "almost every diocese" and "virtually every school".
Ethical? I don't think so. Yet Mr Ratzinger still lectures us about morality, warning young people on Thursday to avoid the temptations of drugs, money, sex, pornography and alcohol. He also disparages celebrity, which is a joke considering that his predecessor, Mr Wojtyla, was the first celebrity Pope. In 1982, I spent one of the most boring days of my life at Wembley stadium while John Paul II celebrated open-air mass. I was there as a journalist, and all I remember is that I read an erotic novel in the press room while Mr Wojtyla denounced "sexual permissiveness".
Mr Ratzinger lacks star quality and he doesn't seem to have worked out how to revitalise the Vatican brand. He finds it so hard to say sorry for the child-rape scandal that admiring commentators are reduced to scouring his pronouncements for "glancing" references that might, with a bit of twisting, be interpreted as an apology. "The revelations for me were a great shock and sadness," he told journalists during his flight from Rome to London. I couldn't help wondering why he was shocked; after all, in his previous job, he was the Vatican official responsible for investigating allegations of sex abuse. Indeed, he's been accused of a cover-up after writing a letter in 2001 to every Catholic bishop, asserting the church's right to hold its inquiries in secret.
Under Mr Ratzinger, the Vatican is as neurotic as ever about sex, condemning consensual relationships between adults and refusing to endorse the use of condoms to reduce the spread of HIV/Aids. When will this sclerotic, celibate priesthood acknowledge that sex is wrong when it's coercive, not when it's between people who aren't married or who happen to belong to the same gender? When will it realise that its claim to the moral high ground has been undermined by scandal and by a puritan disdain that's demonstrably incapable of distinguishing between harmless pleasure and abuse?
Has religion been relegated to the private sphere in the UK? I hope so. I believe passionately in equality – the principle that everyone should have the same rights, regardless of ethnicity, gender or sexual orientation – and a common-sense decency that I've never found in the obscure language of religious texts. As Mr Ratzinger finishes his visit to Britain, I'm celebrating my values – and I just wish my taxes hadn't been used to promote his.