Church leaders say telling children about gay marriage would destroy our society ... ... if we don't what is our society worth anyway?

It wouldn't change their relationship. "Love is love," they say, "and no amount of law or paperwork will change that, nor will any hounding from religious folk. Marriage would show that we are normal, not different, and that we are just as committed as a straight couple."

Sadly, belittling and undermining loving, committed, same-sex relationships is all too common. As recently as 2010, Lord Tebbit said unequivocally: "We should be utterly, completely and absolutely clear that a civil partnership is not a marriage, cannot be a marriage, never will be a marriage and should be treated entirely separately from marriage."

The Christian Institute states: "There are two partners to a marriage because there are two sexes. Marriage is a complementary covenant involving the bringing together of the two sexes not only for the purposes of procreation but also to reflect more fully the image of God."

Insisting that marriage and civil partnership be kept separate and distinct perpetuates the notion that relationships between same-sex couples are different and not as stable, rich or valid as those between heterosexual couples.

It is for this reason that Sam and Pipa, along with many Scots, warmly welcomed the Scottish Government's pledge to consult on extending the legal form of marriage to same-sex couples. For lesbian, gay, bisexual and transgender people, this was at last an indication that our loving, committed relationships would be recognised as every bit as meaningful as those of our heterosexual compatriots. To most Scots it was a clear sign that, in 2012, ours is an open, inclusive and progressive nation.

Stonewall Scotland campaigns for equality and justice for gay men, lesbians and bisexuals. Since becoming its director eight months ago, I have been very clear that any public debate must be conducted by both sides in a respectful and courteous manner. That is why we commissioned independent polling by YouGov, so that the voices of Scottish people – including those of faith – could be heard above the shrill objections of some disproportionately vocal politicians and clerics.

The results were clear. The poll of 1968 people showed that two-thirds of this country's population supports same-sex marriage. Among those aged under 50, that rises to 80%. Crucially, half of people of faith support the proposals – which suggests that the discourse of leading clerics does not reflect the opinions of those gathered in Scotland's churches, mosques, synagogues and temples.

Over the past few months, that discourse has become increasingly vitriolic, and is deeply offensive to gay people and their families. But it also creates an atmosphere of intolerance where prejudice and bigotry can fester – often with tragic consequences. Our YouGov poll showed that three in five people believe that religious attitudes are responsible for public prejudice against gay people.

Within the past few months, leading clerics have compared loving, committed, same-sex relationships to bestiality, slavery and child abuse. Cardinal Keith O'Brien, Britain's most senior Catholic, described same-sex marriage as "grotesque". Frankly, I have been shocked and dismayed at the Cardinal's tone, and feel he has done his office and the church a disservice. Many religious leaders have deliberately and dishonestly asserted that faith organisations will be forced to conduct same-sex marriages against their will. Yet throughout this debate, Stonewall Scotland has been crystal clear that religious organisations which do not wish to conduct marriages between people of the same sex should not be forced to do so.

That is a fundamental issue of religious freedom. However, that principle also means that religious organisations should not try to prevent civic groups from marrying gay couples, nor should they attempt to hinder religious groups such as Unitarians, Quakers and Liberal Jews, which have already expressed a desire to conduct these ceremonies. There are, after all, many gay people whose faith matters deeply to them, and who wish their long-term relationships to be recognised as marriages by their own religious leaders, within their own congregations.

At the beginning of last week, the Scottish Government was expected to announce a decision on whether it would legalise same-sex marriage.

However, on Tuesday afternoon it emerged that the decision had been postponed, and that a subcommittee would now examine how to protect "religious freedom and freedom of speech". There followed a certain amount of intrigue on this issue, with a leaked email seeming to suggest that the Scottish Government will not proceed until the UK Government amends the Equality Act 2010, which guarantees equal protection from discrimination on the grounds of sexual orientation.

Let's be clear: the act as it currently stands ensures the opt-outs that the Catholic Church is calling for. Schedule 23 of the act already states that religious bodies and their staff are exempt from sexual orientation discrimination law – which means the Catholic Church and all its priests are not required to carry out same-sex marriages, since it is against their doctrine. If, however, the Scottish and UK Governments wish to ensure that there is an "avoidance of doubt" clause in the act to provide further reassurances, then I am comfortable with that, as long as there is no delay in introducing a bill to the Scottish Parliament.

The email in question also raised points about what faith schools would supposedly have to teach if same-sex marriage became law. Of course, it is right that we respect the sensitivities around teaching, but it is also right that our schools address the issues of sexuality and relationships. There have been unfounded claims that if same-sex marriage is introduced, children and young people will be force-fed gay propaganda and teachers will be forced to "promote" homosexuality in the classroom.

This is nonsense. No-one would be required to do anything in relation to same-sex marriage that they are not already required to do with regard to civil partnerships.

But I think we need to consider the real issue here. Two weeks ago, Stonewall Scotland published research into homophobic bullying in Scotland's schools. The findings were stark, demonstrating that going to school is a daily nightmare for many young Scots, and bullying is a problem for more than half of lesbian, gay and bisexual young people. One 17-year-old, Scott Gorman, interviewed in this newspaper, had been spat on, had hot soup poured over him, and was made to dress for PE in a separate changing room.

The long-term impact of such treatment can be profound. Scott Gorman, who had hoped to train as a teacher, ended up leaving school early. One-quarter of gay pupils who experience bullying attempt, or think about, taking their own lives as a direct consequence, and more than half deliberately harm themselves. Some 99% of gay young people hear homophobic language on a regular basis. And less than one-third of pupils in Scotland say their schools deal appropriately with this kind of behaviour. Fewer than three in five said their schools described such bullying as wrong.

The mark of a society is how it treats its young people. It is deeply worrying that many teachers and schools still fail to challenge homophobic bullying effectively. Discussing same-sex marriage, and the fact that families in modern Scotland come in all shapes and sizes, is critical to ensuring that young people feel safe and secure at school.

Stonewall Scotland provides teachers with age-appropriate materials that enable them to sensitively discuss different families with their students. Those resources are designed to help schools celebrate difference so that all children can feel proud to talk about where they come from, and enjoy learning in an unthreatening atmosphere.

For Scotland to prosper we must all work to build a country where every young person – regardless of their sexual orientation – can grow up to fulfil every ounce of their potential. If we are to compete in a 21st-century world, we have to create a society where all citizens are prepared to work, live and pray alongside people of different faiths, ethnicities, nationalities and sexual orientations.

Our organisation works with some of the country's largest employers – including Clydesdale Bank, Lloyds TSB Scotland and the Scottish Government – to help them promote diversity and improve their workplaces for gay staff. In the process, we've learned that this approach is actually good for business.

When people can be themselves, and feel valued and respected, their performance – whether in the classroom or at the office – reflects their full potential.

And that's what the campaign to secure equal marriage in Scotland is about: allowing people to be themselves and to be with the people they love with exactly the same rights that everyone else takes for granted.

Let's not forget that we've heard these arguments from opponents of equality at every moment of progress. When civil partnerships were introduced we were told the sky would fall down and society as we know it would cease to function. Of course, the reality is simply that loving, committed, same-sex couples were able to commit to one another and the rest of us had to navigate an extra trip to select a gravy boat from the John Lewis wedding gift list.

I know that progress is never inevitable. A couple of weeks ago, the Catholic Church in Scotland pledged to raise an extra £100,000 to defeat this modest measure for equality.

"Marriage is under threat and politicians need to know the Catholic Church will bear any burden and meet any cost in its defence," said Cardinal O'Brien, adding that Scotland's bishops have designated August 26 as "Support Marriage Sunday" – an "opportunity to remind Catholics of the importance of marriage as a union of a man and a woman".

Today being Sunday, congregations will be gathering in churches across Scotland. Many people sitting in the pews will reflect that £100,000 could have funded calls from 25,000 children who urgently needed to escape abuse, or given shelter to 4000 homeless people for a night. And the vast majority of Scots will wonder why a man who states that he is a Christian has declared war on another group of people in Scottish society.

Over the past few days, we have heard desperate accusations that Stonewall Scotland has spent millions of pounds of public money campaigning for equal marriage.

All our campaigning work is funded by the generosity of thousands of individual supporters. We do not seek or use public money to campaign for equality. Cacophonous bigotry cannot be allowed to determine this issue, so it's vital that we allow the voices of the equality-minded majority to be heard.

Creating matrimonial equality would be a modest step for Scotland, and it needs to be implemented soon. There are those – such as former SNP leader Gordon Wilson – who argue that the eve of a constitutional referendum is no time to be talking about same-sex marriage, and that the proposal would "alienate" those considering voting for independence.

But this issue goes far beyond politics. Now, more than ever, the Scottish Government can demonstrate strong and decisive leadership by introducing legislation before the referendum. By doing so, they can set out a vision of an inclusive and progressive Scotland where every citizen is valued and respected.

Colin Macfarlane is director of Stonewall Scotland

www.stonewallscotland.org.uk