The ‘bus advert storm’ confirms that Christians are now more progressive than gay rights activists

Stonewall's advert shares the same view on homosexuality as 19th century Christians

The fuss over the anti-gay bus advert confirms that there has been an extraordinary shift in the debate about homosexuality. Once upon a time, conservatives and Christians argued that homosexuality was a genetic trait, while gay-rights activists insisted it was a lifestyle choice. Now, in an eye-swivelling turnaround, their arguments have reversed. Surely, this is the most comprehensive position swap in the history of culture wars?

The reason the bus advert riled gay-rights activists was because it implied that homosexuality is a phase that some people go through – one that can be rectified with therapy. The ad was designed by a Christian outfit called the Core Issues Trust in response to a Stonewall ad. It reads: "Not gay! Ex-gay, post-gay and proud. Get over it!" Transport for London has now blocked it.

The ban has delighted gay activists since they claim it is wrong to depict homosexuality as something "freely chosen". The assumption is that the Christian lobby is backward and the gay-rights lobby is correct. But is it really?

The idea that homosexuality is a determined trait is new in gay-rights activism. It would have been anathema to the gay campaigners of yesteryear. Indeed, they once kicked against the idea. In the bad old days, the conservative side claimed homosexuality was "an involuntary physical condition", arguing that there was something different in the "cerebral cortex" of homosexuals – that they were somehow diseased.

Today's trendy belief in the "gay gene" echoes these old ideas about a "gay germ" that carried through to the 1950s. We see this in 1955 when the British Christian theologian Derrick Sherwin Bailey described gayness as "an inherent condition" with “biological, psychological or genetic causes”. And then again, as late as 1980, when Catholic writers like the American John Boswell (who was very sympathetic to homosexuals) referred to homosexuality as something that was "biologically predetermined". So for much of the twentieth century it was only those who were disgusted, confused or pitying of homosexuals who thought it was biological.

The old gay-rights campaigners challenged the notion that it was genetic and instead put forward "the lifestyle choice argument", as argued in Robert Alan Brookey's book. Gay liberationists didn't sheepishly argue that they couldn't help being gay, but rather asserted that they should be free to pursue any lifestyle they wanted. As Brookey says, "only recently has the gay-rights movement embraced the biological argument". This embrace happened in the 1990s when the so-called "gay gene" was discovered. It was cheered by gay-rights activists. Their use of this argument created an extraordinary defensiveness in the gay-rights movement, which now says "we can't help the way we are" rather than simply "let us be free".

Bertram J. Cohler et al argues that the biological argument is used as a "dodge" by gay campaigners, saying: "An entirely biological explanation for [homosexuality] spares all concerned the anxieties associated with questions of meaning, morality or ambiguity". That is, gay activists have ditched the hard moral argument for gay rights, preferring to adopt the easy claim that gays are born, not made. This spares them the hassle of challenging people to accept that adults should be free to live their lives as they see fit.

So now we have the utterly bizarre situation: Christians claim homosexuality is a matter of agency, while gays claim it is innate. I have no doubt that Core Issues Trust is a weird outfit and its gay-fixing therapy is hocus pocus (which is still no excuse for banning its ads).

But you know what? In emphasising the elements of choice and agency in the homosexual lifestyle, these Christians display more humanity than those who claim that homosexuality is a genetic condition.