Members of the Catholic L.G.B.T. community and their families gathered in a San Diego church on Saturday to celebrate Mass and observe the 20th anniversary of a letter from bishops meant to address the pastoral needs of Catholic parents with gay and lesbian children.

“‘Always Our Children’ was written at a time when good and faithful churchgoing Catholics were witnessing society quickly change before their eyes and the church seemed—in their eyes—to stand still,” Bishop John Dolan, an auxiliary bishop in the Diocese of San Diego, preached at St. John the Evangelist Church, located in San Diego’s historically gay-friendly Hillcrest neighborhood.

The U.S. bishops’ committee on marriage and family released the letter “Always Our Children” in 1997 as an attempt to encourage parents not to abandon their gay and lesbian children and to assure them of God’s love. It received mixed reactions at the time, with some Catholics decrying it as a capitulation to the still-nascent gay rights movement while others said it did not go far enough to combat bigotry in the church and wider society.

The U.S. bishops the letter “Always Our Children” in 1997 as an attempt to encourage parents not to abandon their gay and lesbian children.

During his homily, Bishop Dolan recalled the varying results some Catholic parents experienced when seeking pastoral advice from priests about how they should respond when a child came out as gay or lesbian.

“In many of these encounters with pastors, parents were met with love and compassion as they discussed their children’s ‘new way of life,’ while—sadly—others were met with words of condemnation; even if the hard words of their pastors were meant to express truths regarding their children,” he said.

Aaron Bianco, a pastoral associate at the parish who planned the event, said he was heartened by the number of families and L.G.B.T. Catholics who attended the Mass—including a couple of dozen Catholics from Palm Springs, Calif., who drove three hours to attend.

“You could see people crying,” he told America, recalling how one person in attendance confided to him that he had not been to Mass in nearly three decades. He said some parents, especially from the Hispanic community, had told him they felt as though they had to distance themselves either from their church or from their gay children, a choice he tells them they do not need to make.

Bishop Dolan used part of his homily to urge sincere dialogue, which he acknowledged can be difficult when discussing heated topics.

“We want them to know you don’t do either. You can love your child and be an active member in the church,” he said.

While the Mass was originally advertised for the parents of gays and lesbians, in honor of the original letter, many gay and lesbian Catholics also attended after diocesan and parish staff reached out to the L.G.B.T. community.

Kyle Escobar-Humphries, who attended the Mass with his husband, told The San Diego Union-Tribune, “It’s important because my kids have two gay dads and I would like for them to understand that this church is open for everybody.

“I want them to understand how to treat each other equally,” he continued.

Bishop Robert McElroy, who leads the diocese, also attended the Mass. He told the Union-Tribune that the Mass was a response to Pope Francis’ call for the church to serve everybody.

“Pope Francis is calling us to reach out to everyone with a message of radical inclusion.”

“Pope Francis is calling us to reach out to everyone with a message of radical inclusion,” he said. “Sadly, there has been an estrangement and an alienation with L.G.B.T. people, and the church needs to take steps to heal that.”

The event came at a time when some Catholics are debating how welcoming the church should be to Catholics who do not adhere to church teaching on sexuality. The debate received a jolt of energy in 2013 when Pope Francis asked, “Who am I to judge?” when asked about gay priests. It was renewed more recently with the publication of Building a Bridge by James Martin, S.J., an editor at large at America, in which he argues that church leaders should be more welcoming to L.G.B.T. Catholics and that they in turn should be more respectful toward church leaders.

That book has set up a sharp debate, with several cardinals and bishops, including Bishop McElroy, endorsing the book’s message, but it has also received a wave of negative feedback from some critics, who argue that the book does not more fully explain Catholic belief that sex between two people of the same gender is a sin.

Bishop Dolan used part of his homily to urge sincere dialogue, which he acknowledged can be difficult when discussing heated topics.

“Twenty years later, the dialogue and discourse continues, but it isn’t always fruitful or civil. The unshaking ideologies of people without and within the L.G.B.T. community are daily blogged, tweeted and Facebooked in ad hominem, yellow-journalistic, fake-news style where now the mysteries of Christ and the Good News are lost and good people are directly or indirectly hurt,” he said. “Such rhetoric has to stop!”

“Ad hominem attacks and lies about those with whom we disagree must always be avoided,” he continued. “As our Catechism states, ‘If a lie in itself only constitutes a venial sin, it becomes mortal when it does grave injury to the virtues of justice and charity.’ Civil discourse and fruitful dialogue cannot be forfeited by those who uphold the teachings of the church and/or by those who struggle to incorporate our teachings within their personal lives.”

Mr. Bianco said he had received multiple threats in the weeks leading up to the Mass.

The Mass itself, which was attended by more than 400 people, was not without controversy.

Mr. Bianco said he had received multiple threats from people posting on Catholic websites in the weeks leading up to the Mass and that the tires on his car had been slashed in the church parking lot. As a result, more than three dozen police officers were on hand in case of violence.

But in the end, only a small group of protesters gathered outside the church, distributing pamphlets decrying the message of “Always our Children,” according to the Union-Tribune.

One protester accused the church of watering down its teaching on sexuality.

“The church is bending with the times and with the pervasiveness of homosexual activism throughout the country and indeed the globe,” Allyson Smith told the newspaper. “And we feel the church should stand strong as a bulwark against cultural trends…. Our concern today is the church is becoming too accommodating to homosexuality.”

But Mr. Bianco said that in his eyes the Mass was a success.

“Members of the community know that at St. John’s, in the neighborhood where they live, the doors are wide open and we’re always welcoming them,” he said.