As protests go, it was one of the stranger ones. Several thousand people from around Ireland lined the streets of Dublin at the weekend to fight for an issue that isn't being discussed in parliament or by the media or on the streets. The benignly titled Rally for Life was an anti-abortion protest made up of parents with young children, priests, nuns, pensioners and teenage girls, and it was a key part of the ongoing passive-aggressive abortion war that's being fought in Ireland.

The march itself was billed as a family day out. There were facepainters, a red open-top double-decker bus laden with balloons, and bright yellow T-shirts for participants. Hundreds of placards had giant smiley faces with the slogan "Protect Life" written on them. Others read: "Enda [Kenny, the Irish prime minister], keep your pro-life promise". Parents were encouraged to bring their children along, and many did. A Facebook page afterwards showed photos of teenagers with big smiles enjoying their first anti-abortion march.

But beneath the carefully manufactured surface, this was a pre-emptive and deliberate flexing of political muscle to warn politicians that there is an organised and well-funded radical anti-abortion lobby in Ireland, which will fight hard against any attempt to loosen some of the strictest abortion laws in the western world.

Abortion is generally illegal in Ireland but a constitutional loophole means that it is not always illegal. The supreme court in 1992 ruled that abortion is allowed if the mother's life is in danger (including a suicide risk). However, successive governments have cowered away from legislating on the decision, leaving a massive grey area: because there is no law covering it, there are no guidelines on who can obtain an abortion, and doctors have no framework on what they can and can't do to advise women effectively. In December of last year the European court of human rights issued a judgment and compelled the government to act on this grey area, and the new coalition government has announced a plan to set up an expert group by the end of the year to examine this. In the meantime, however, it is estimated that 12 Irish women travel to the UK every day (4,402 last year) to terminate a pregnancy.

Saturday's march was a deliberate part of the ongoing rebranding of the radical anti-abortion lobby to move away from its image of a dogmatic, fiercely Catholic movement. But elements remain: some protesters held rosary beads and waved pictures of the Virgin Mary at a smaller pro-choice march, which was held at the same time. Priests in cassocks walked alongside groups of teenagers. Some protesters held signs conflating abortion with sodomy.

The religious left, meanwhile, has by and large stayed out of the abortion debate, organising instead around issues such as poverty and social exclusion. Unlike in Britain, with its vocal tradition of the religious left, the Catholicism which once saturated Irish society has had such a strong lingering effect that even the Labour party – now in government – has taken a softly softly approach to abortion.

The government has a prime opportunity now to take the small but crucial step of legislating to allow abortion in Ireland when a woman's life is in danger. Currently still enjoying a honeymoon period since March's general election and the much-praised state visits of the Queen and President Barack Obama, there are no elections due until at least 2014 so political pressure is off. If it chose to, it could finally fix this. It has the support of the people: surveys show more than three-quarters of the population support allowing abortion if the mother's life is in danger. Other surveys show more than half of people under 35 favour the introduction of abortion more generally.

These more moderate voices – on both sides of the debate – need to be listened to. Instead, the discourse is often hijacked by emotive language and religion, as with Saturday's march, to stop any real debate from happening. This happened with the three previous abortion referendums in Ireland and, if the Rally for Life is an indicator, is in danger of polluting future debates.

Legalising abortion is still a long way from happening. Abortion debates in Ireland have always been quagmires and there is little stomach for them, even if the country wasn't currently battling its economic crisis. But the government now has an opportunity to make small but significant progress in the area – as long as it refuses to kowtow to the religious right.