How did same-sex marriage become such a major issue so quickly? Only a decade ago, almost no-one thought it was an important topic. Now, to hear certain people tell it, it is a civil right as vital as the right to free speech or the right to vote.

How did this happen? Brendan O’Neill (pictured), who gave a talk to the Iona Institute last year on anti-Catholicism, suggests an intriguing answer in a provocative blog for the Telegraph website. O’Neill suggests that the reason that it has become such a fashionable issue is  “because it is so very useful as a litmus test of liberal, cosmopolitan values”, a way to separate themselves from the ‘unenlightened’.

He points out that same-sex marriage “has achieved this hot-potato status without the benefit of a mass movement demanding it, far less any public streetfighting or serious civil unrest by homosexuals determined to get hitched”.

He writes: “For all the self-flattering comparisons made by gay activists between their demand for gay marriage and black Americans’ demand for civil rights in the 1950s and 60s, it is the differences between these two things that are most striking. Gay-marriage activists have not had to march for years on end, carry out mass boycotts, face water cannons, get attacked by dogs or run the risk of being thrown in jail for their campaign to achieve almost saintly status, winning the backing of leading politicians and commentators.

“The speed and ease with which gay marriage has gone from being a tiny minority concern to become the No 1 battle in the modern culture wars has been truly remarkable – and revealing.”

Instead of being a response to a popular demand for rights, O’Neill suggests that supporting gay marriage “has become a kind of shorthand way of indicating one’s superiority over the hordes, particularly those of a religious or redneck persuasion”.

He says: “The use of gay marriage as a platform from which to announce one’s superior moral sensibilities can be seen in the way that its backers, those ostensibly liberal reformers, look down with undiluted snobbery upon their critics and opponents.

“Those who are against gay marriage, whether it is Catholic bishops or conservative politicians, are not seen simply as old-fashioned or wrong-headed, but as morally circumspect, possibly even evil. They are even branded as mentally disordered, being tagged as ‘homophobic’ (that is, possessed of an irrational fear) if they so much as raise a peep of criticism of gay marriage.

“Indeed, liberal campaigners frequently claim that gay marriage, unlike every other issue in the world, is a straightforward black-and-white matter on which there is only one right answer – “yes”. As a writer for the Guardian puts it, ‘There are some subjects that should be discussed in shades of grey, with acknowledgement of subtleties and cultural differences. Same-sex marriage is not one of those. There is a right answer.’

“That is, there is no room for nuance, disagreement or even for debate when it comes to gay marriage – instead, paraphrasing George W Bush’s post-9/11 splitting of the world into good and evil camps, for many gay-marriage activists you are either for gay marriage or you are a lowlife.”

Incidentally, O’Neill is an atheist, and has not made up his mind on the issue of same-sex marriage.