The religious notion of sin that has helped shape the American legal system’s view of gay and lesbian rights took a hit with Friday’s Supreme Court decision legalizing same-sex marriage across the country.

The decision yanked that linchpin of moral disapproval from the nation’s marriage laws, leaving many Roman Catholics, Mormons, Baptists, Methodists, Orthodox Jews, Muslims, evangelical Christians, and other people of faith who oppose same-sex relationships in conflict, rather than unity, with the nation’s legal and social order.

”There’s long been a deep Christian cultural and legal influence in this country, and it survives most strongly in the most religious parts of this country, namely the South and the Midwest,” said David Gushee, a Baptist and professor of Christian ethics and director of the Center for Theology and Public Life at Mercer University in Macon, Ga. “It’s hard to overstate the level of anguish and fear on the part of many conservative Christians about what this decision and the overall direction of the culture on this issue might mean for them. They’re very worried.”

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American churches have been on the front line of the gay civil rights battle since its beginning, both as a bulwark of opposition and as a sanctuary for lesbian, gay, bisexual and transgender people.

In its amicus brief filed with the court in the marriage decision, the US Conference of Catholic Bishops warned that expanding marriage rights will “create church-state conflict for generations to come,” by threatening individuals, businesses, and religiously affiliated nonprofits with discrimination charges if they exercise their religious objections to same-gender marriages, a view stated by Chief Justice John Roberts in his dissent to the same-sex marriage decision Friday.

In 2008, Mormons were critical to winning passage of Proposition 8 in California, which banned same-sex marriage. But many denominations have long welcomed gay people, including Unitarians, the United Church of Christ, the Reform Jewish Movement, Quakers, and Episcopalians. Earlier this year, the Presbyterian Church USA endorsed same-sex marriage.

A survey this month by the Pew Research Center found that 57 percent of Americans now approve of same-sex marriage, driven by the Millennial generation of young adults. But the survey found that “one of the strongest factors” among those opposed “is religion, and the sense that homosexuality is in conflict with one’s religious beliefs.”

White evangelical Protestants, Pew found, “stand out for their deep opposition” to same-sex marriage, with 70 percent disapproving, most of those strongly. At the same time, Pew found that personal acquaintance with gay or lesbian people is strongly linked with approval of their marriages. Both factors are playing out now in American churches.

Gushee, who will speak at San Francisco’s Grace Cathedral on Thursday in celebration of the marriage decision, said he came from the traditionalist Christian position but changed his views with exposure to LGBT Christian friends and the coming out of his lesbian sister.

He was troubled that young gays and lesbians especially were not allowed within traditional Christian thinking to integrate their sexuality and spirituality, leading to “a lot of inhumane and sometimes quite terribly destructive outcomes for individuals and families,” he said. “So religion, my religion, the religion that I cherish and that I practice and teach, was producing consistently toxic outcomes in people’s lives.”

The Episcopal Church was engulfed in more than a decade of internal struggle of the kind that continues to split such mainline Protestant denominations as the Methodists. “There was tremendous anxiety, a lot of anger, a lot of fear,” said the Right Rev. Marc Handley Andrus, bishop of the Episcopal Diocese of California, whose seat is at Grace Cathedral. In 2012, the church approved a liturgy for blessing same-sex relationships.

”The Episcopal Church was the first major denomination in the Bay Area to stand up in the beginning of the AIDS crisis and to say this is not a punishment of God against gay people,” Andrus said. “Grace Cathedral was burying 35 people a week during the height of the AIDS crisis in San Francisco,” giving gay men and women “the dignity and love of Christian burial.”

Other denominations, such as the Southern Baptist Convention, are digging in.

”Some secular Americans assume that evangelicals and Roman Catholics and others will simply get over our views on marriage and sexuality now that the culture has changed,” said Dr. Russell Moore, president of the Southern Baptist Ethics & Religious Liberty Commission. “They’re wrong.”

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Pro-gay theologians trace the history of religious animus toward homosexuality to a literal interpretation of a handful of Bible passages. These include an Old Testament passage from Leviticus that calls two men having sexual relations an “abomination” that should be punished by death, and, in the New Testament, a part of Paul’s letter to the Corinthians that condemns homosexuality.

That biblical view has been deeply embedded in American culture and law, said the Rev. Jasmine Beach-Ferrara, a minister in the United Church of Christ and executive director of the Campaign for Southern Equality, which fought for same-sex marriage.

”There’s a conjoining of religious cultural power and political power” in the South, especially where religion has been “the first line of rationale for the whole system of homophobic and transphobic laws and belief systems and practices,” Beach-Ferrara said.

Many traditional churches hold biblical authority as sacred. The Bible starts with the story of Adam and Eve, establishing “a male-plus-female sexuality paradigm” that implies that “anything else is not quite right,” Gushee said. “So if people are not living according to that, there is something wrong with those people.”

The Bible spans thousands of years and many cultures and languages, containing nearly 32,000 verses, with just over a dozen seeming to condemn same-sex relationships, Gushee said.

Resistance to same-sex marriage will continue in many churches.

”We believe that marriage and sexuality are revealed truths handed down to us by Jesus and his apostles and we don’t have the authority to change or to capitulate on those things,” said Moore of the Southern Baptist Ethics & Religious Liberty Commission. “But what has changed is we can’t assume that the people in the neighborhoods around us agree with us on marriage or even understand what we’re talking about.”

Story distributed by the New York Times News Service.