MARY McAleese has said homophobia should be consigned to history in Northern Ireland.
The former Irish president accused those who sought to convert gay people of damaging the vulnerable.
Mrs McAleese, the mother of a gay son, said significant numbers of teenagers were afraid to go to school for fear of being picked on.
Northern Ireland is the only part of the UK or Ireland where same-sex marriage has not been legalised.
In a Belfast speech, Mrs McAleese said: "I am now a grandmother to two very small boys. I want them to grow up in peace and in a fair and decent world where the entire architecture of homophobia and of anti-LGBTI (lesbian, gay, bisexual, transsexual and intersexed) attitudes and practices has been completely dismantled and consigned to history.
"That will not happen by chance but by change."
She said Ireland's Yes vote to marriage equality last year sent a signal of goodness and decency.
The Belfast-born former head of state claimed gay rights campaigners were making history.
"You are turning the tide of hurt and hatred, country by country, culture by culture, heart by heart.
"It is helping our world to experience the liberating joy that comes from taking down the edifice of homophobia brick by brick, the bricks of tradition, doctrine, dogma, beliefs, attitudes, practices and laws.
"Only when that edifice has crumbled like the walls of Jericho will we vindicate the generations of countless LGBTI men and women, whose lives were only half-lived and whose dreams of acceptance and full equality were never realised."
The founder member of the campaign for gay rights 40 years ago received a "Tolerantia" award from international LGBT organisations during the Belfast ceremony for her work combating homophobia.
She said: "It is important also to remember where we are at historically in the dismantling of the architecture of homophobia.
"It is global in its reach. It has a still unyielding grip on many minds, on influential institutions, on entire religions and faith systems, on governments, on cultures, on laws and attitudes. Even in the most accepting of places, it makes life somewhere between tough and intolerable for many."
She said gay people were still vulnerable to being damaged by those who are mustering the forces of "last-stand resistance" to equality through laws that would push back the boundaries of their freedom.
"I have met them and listened to them, the ministers, the priests, the amateur and the professional psychologists, the doctors, the therapists, the politicians and the theologians who preach and practice this snake-oil conversion or reparative therapy.
"They need to be challenged for they are inflicting damage in and through therapy centres, clinics, seminaries, lecture theatres, conferences and all the other places where they are insidiously peddling their wares."
