Some people think differently from you - why not just get over it?

It strikes me as ironic that the logo for the "ex-gay" Christian charity, Core Issues Trust, is a partially intact apple. If that doesn't evoke the filthy delights of giving in to temptation, yielding to the forbidden fruit, then I don't know what does. Yet the charity, which is based in Northern Ireland, advocates the opposite course of action: controversially, it offers support to people who want to resist, diminish or eliminate feelings of same-sex attraction.

To this end, in April 2012, Core planned an advertising campaign on London buses, featuring a poster that proclaimed: "Not gay! Ex-gay, post-gay and proud. Get over it!" This was intended as a response to a previous bus advert by Stonewall, the British gay rights group, which read: "Some people are gay. Get over it!" But the Core posters never appeared. Two hours before they were due to go public, the London mayor, Boris Johnson – who was in the final stages of his re-election campaign – appeared to intervene, stating: "London is one of the most tolerant cities in the world and intolerant of intolerance. It is clearly offensive to suggest that being gay is an illness that someone recovers from and I am not prepared to have that suggestion driven around London on our buses." Clearly he was expecting loud cheers and, to a large extent, he got them. Goofy, loveable Boris, foppish and fearless, giving the loopy Bible-bashers what for.

The ensuing legal row is still going on. In January of this year, Core claimed a partial victory when the Court of Appeal called for an investigation into Johnson’s role in banning the advert, but the case is complex and may well end up going to the European Court of Human Rights. It’s worth watching, however, because it says a great deal about what exactly constitutes tolerance these days. (Clue: it looks a lot like its opposite.) You know something is badly awry when an act of political censorship is welcomed as a gesture of decent, right-thinking open-mindedness. Treating such adverts as a form of secular blasphemy, which must be erased by the authorities for the moral health of the people, shows a disturbing disregard for democratic freedoms, as well as a lack of confidence in the public’s own powers of critical judgment.

In the current cultural climate, with its popular enthusiasm for gay rights, saying you don’t want to be gay seems at best ungrateful, and insulting to happy homosexuals, at worst deeply deluded. If you go further and insist you have overcome your unwanted same-sex inclinations, as Core director Mike Davidson claims, and consider yourself “ex-gay”, prepare to be treated as a social outcast, scourge of the “liberal” majority. You are someone we can all despise, relishing that tribal solidarity that comes from knowing we’re right and you, over there, on your own – well, you’re wrong. Truly, there’s no man more lonely than a post-gay preacher.

I hasten to say, of course, that I remain unconvinced by the ex-gay lobby’s arguments. There’s no evidence gayness can be prayed away, or wiped out by psychiatric intervention. Even Alan Chambers, former president and poster boy of Exodus, the world’s biggest ex-gay organisation (now defunct), has acknowledged “the shame and guilt you felt when your attractions didn’t change”, and apologised for the harm his group caused. So don’t imagine these words are some kind of defence of the rights of bigots to exercise their homophobia with impunity; there is no Bible hidden up my jumper.

But here’s the vital thing: if consenting adults want to try to suppress aspects of their sexuality, that’s none of my business, or yours. I may consider it to be a joyless, fruitless endeavour, but that’s irrelevant. How such people self-identify is up to them, and they are entitled to describe themselves in whatever way they choose. If they want to shout about it from the rooftops, or indeed emblazon it on the side of a bus, that’s their right. That’s what freedom of expression looks like. Who cares if some people find it offensive? There are more important principles at stake. Get over it!