Three people stick in my mind. Scott, whose marriage was breaking up and was taking drugs to cope; Beth, a heroin addict whose new-born baby had withdrawal symptoms; and 19-year-old Peter, who fell out with his parents and was living in a hostel and drinking every night. All three of them were going through a hell of a time and all three of them were hoping they could be saved by religion.

And on the face of it, they were. Scott joined a church and became drug-free. Beth managed to reduce her methadone and moved into a new house with her daughter. And Peter patched things up with his parents. Peter also told me there was a time when he prayed for tickets to a sold-out Hibs game and God delivered them. There’s a river, Peter told me, and the tide is the way God wants you to go.

But there’s a catch, and it’s well hidden. I met Scott, Beth and Peter on a Christian course at a church in Glasgow. You’ve probably heard about it: it’s called the Alpha Course and it’s a religious phenomenon, a beginner’s guide to God that has converted thousands of people across denominations. I signed up for it to find out how it works in practice and I met Scott, Beth and Peter (I’ve changed their names) and lots of other people who were mostly vulnerable in some way and mostly looking for help and guidance.

The help they received worked in its way: being in the church helped them get their lives sorted. But I was concerned – though I shouldn’t have been surprised – about what some of the leaders were saying. Nicky Gumbel, the man behind the Alpha Course brand, told me the meetings were designed to be unpressurised, but that the rules were clear: sex outside marriage and practising homosexuality are sins. "Our arguments on that are the same as those of every major denomination,” Gumbel told me.

The result is an almost impossible mis-match: a course which promises to awaken your spirituality in a non-threatening way but ultimately says: be gay if you want to, but don't – repeat don't – do anything about it. "What we’re trying to do,” said Gumbel, “and I know this is a very difficult balance, is to retain the message of the Christian faith which we believe is unchanging, but to present it in a culturally relevant packaging."

The consequences of that approach are clear, I would have thought. One minister, who’s gay, told me liberal churches like his are often left to pick up the pieces with lesbian and gay people who’ve gone on these kind of courses. “They are attracted by the initial buzz of friendship and support,” he said, “but what the course doesn't say at the outset is that it has no place for same-sex relationships. It is a recipe for an empty and guilt-ridden life."

So what can be done? Boris Johnson said this week that his government would definitely be banning gay conversion therapy, which tries to change a gay person’s sexuality or behaviour. The PM said the practice had no place in the UK and it was great to hear him say it, although it was also worrying to hear him say the ban would be introduced after a “study”, which, as we know, is the politician’s strategy for appearing to do something while not doing anything.

However, the bigger problem is that a ban won’t achieve very much. Earlier this month, the Catholic Church in Scotland was accused of supporting a form of conversion therapy by promoting a programme which counsels gay men and women to remain celibate. The Church said it was opposed to gay conversion therapy but did provide support for “those experiencing same-sex attraction who want to grow in holiness by living chaste lives”.

It is that sort of approach – one I saw for myself on the Alpha Course – that will not be changed by any ban on conversion therapy. Therapists who specifically promise to “cure” sexuality will be banned, but otherwise many churches will carry on promoting the belief that gay people must be celibate and it doesn’t matter if they do it in seemingly friendly and no-pressured way – the damage to vulnerable people will still be the same.

On the plus side, of course, there is religion’s power to do good. Beth was convinced the cure for her addiction was a mixture of methadone and Christianity. Scott’s marriage was saved. And Peter believed God could get him tickets for a Hibs game. But how are we to judge a church if it helps some people through addiction, divorce, and breakdown, but forces others into a life that could do them serious emotional damage?

All columnists are free to express their opinions. They don’t necessarily represent the view of The Herald.