Gay people in the Catholic Church are sometimes "treated like dirt", according to a priest invited by the Vatican to address a conference on families in Dublin on Thursday ahead of a visit by Pope Francis.
US Jesuit priest James Martin preaches openness towards gay Roman Catholics -- in the face of some traditionalists who have tried to shut him down.
He spoke at the 2018 World Meeting of Families (WMOF) in Dublin, a global Catholic gathering that takes place every three years, which opened on Tuesday.
"The inclusion of a talk called 'Showing Respect and Welcome in Our Parishes to LGBT Catholics and their Families' is a huge step forward," Martin told AFP.
"It is a sign to all Catholics that the Vatican considers LGBT Catholics part of the Church," said the author of a bestselling book which reaches out to lesbian, gay, bisexual and transgender Christians.
Pope Francis closes the WMF on Saturday and Sunday.
The gathering has featured talks and speeches, including that given by Martin, who runs the Jesuit magazine entitled America.
However, several groups, including the Global Network of Rainbow Catholics, which brings together LGBT associations from around the world, said they have been denied a platform.
Meanwhile, the Irish branch of a traditionalist US Catholic movement had called for the Archbishop of Dublin to cancel Martin's visit.
"What kind of Jesuit would I be if I let online hatred prevent me from speaking about compassion?" said the priest, who has also been targeted with a boycott in the United States.
- Insulted from the pulpit -
The pope's visit to Ireland to celebrate families inevitably revived the debate on homosexuality and the Church, especially given that Ireland voted to legalise same-sex marriage in 2015.
Pope Francis sticks with Church tradition on marriage: the union of a man and a woman to procreate.
"Today -- it hurts to say this -- we talk about 'diversified' families: different types of families... But the human family as an image of God, man and woman, is only one," he said in June.
But in 2013, just months after assuming the papacy, he said: "If someone is gay and is searching for the Lord and has good will, then who am I to judge him?", signifying a softer tone.
Martin deplores the Church's treatment of homosexuals in certain countries as "pariahs" in their own parishes.
"I've heard the most incredible stories of LGBT people being treated like dirt," he said.
"They are often insulted: both publicly, from the pulpit, and privately, in one-on-one conversations."
He added: "I'm not challenging any of the church teachings on homosexuality. But we do have to ponder why so many LGBT Catholics have set aside church teaching."
- Change of tone -
Martin said Pope Francis's stance on homosexual relationships was the same as that of his predecessors.
"What has changed is the tone, approach and language," he said.
"His five most famous words may be 'Who am I to judge?,' which were first said in response to a question about gay priests, and were later expanded to include all gays.
"Francis is the first pope, for that matter, to even use the word 'gay'."
Martin continued: "I would not categorise him as a 'progressive' but simply as a compassionate man.
"Pope Francis is trying to reach out to those on the margins both in society -- refugees, migrants, the poor -- and in the Church.
"And in the Church there is no one more marginalised than the LGBT person."
Irish Prime Minister Leo Varadkar, who is openly gay, was a strong backer of legalising same-sex marriage in the country's 2015 referendum.
He has pledged to press the cause of gay and single-parent families with Pope Francis when he meets the pontiff on Saturday.