"Two types of country are moving to embrace gay marriage: the Scandinavian [social democracies] and ones trying to escape a Catholic past that was authoritarian: Uruguay, Argentina, Spain, and [authoritarian to a lesser extent] Ireland," he says.
The central issue for opponents is not so much the marriages themselves, but the concept of family – with children at the center of the battleground.
"Attached to genderless marriage is genderless parenting and the severing of the natural, biological tie. It's an explicit denial of this," Quinn says.
Campaigners see things differently.
Moninne Griffith of Marriage Equality says civil partnerships for gay couples, which began in Ireland in 2011, were a move forward but are not true equality.
"People in Ireland know what separate but equal means," she says, referring to anti-Catholic discrimination prior to Irish independence and in the Northern Ireland of old.
"It's 10 years since [the first same sex marriage case] in the High Court. Even before then the Equality Agency issued a report on equal recognition of same sex relationships."
Ms. Griffith says there is overwhelming public support for the extension of marriage rights, though it is not high on many people's list of priorities.
Desire for a life-marking milestone
Ross Golden-Bannon, a restaurant critic, says he has no immediate plans to get married, but welcomes the Constitutional Convention's decision as an indication of a sea change in public opinion.
"Personally, I'm not in a relationship at the minute, but the big thing for me is, as a gay teenager, I didn't have the same life-marking milestones to look forward to as everyone else. That's quite psychologically damaging," he says.
The issue isn't quite as simple as a left-right divide, though it is fair to say that most opponents tilt conservative, while most supporters tilt liberal. Political support is near-universal, though.