In the political battle over LGBTI rights, social conservatives bent but didn’t break as the Republican party drafted its 2016 platform.

With the campaign of the presumptive nominee, Donald Trump, relatively unengaged in the platform process, Republican activists from across the country spent Monday hashing out their differences on same-sex marriage and other thorny social issues ranging from transgender bathroom access to Internet pornography.

In a cavernous downtown convention center, Republicans spent 12 hours of their two-day marathon to determine the party’s policy manifesto for the coming election in small subcommittees and before a televised assembly of a full committee of 112. The meetings were at times contentious but rarely adversarial.

The proposed language in the platform – which called for a constitutional amendment to overturn the supreme court’s decision in Obergefell v Hodges, which ended all state bans on same-sex marriage – represented a notable shift from past years. In 2012, the platform called for a constitutional amendment to legally define marriage as “the union of one man and one woman”.

Tony Perkins, a delegate from Louisiana and head of the Family Research Council, pushed back at the idea that the change in language represented a change in Republican policy. “The idea that the RNC is walking away from this is not correct – simply addressing the present realities of where the issue stands,” he said. Perkins instead saw it as a Fabian retreat. “You don’t have the votes in the Senate to pass a marriage amendment defining marriage for the entire country ... you have three-quarters of states defining marriage, and states are still ticked that 50m votes were thrown out by five unelected judges.”

However, even that slightly softened language met a vocal effort from delegates seeking to strip any support for a constitutional amendment about same-sex marriage from the platform and instead replace it with neutral language. “We encourage and welcome a thoughtful conversation among Republicans about meaning and importance of marriage,” the amendment reads. Despite an emotional plea from Rachel Hoff, the first openly gay member of the RNC platform committee, the amendment appeared to receive the support of only about 20 of the committee’s 112 members and fell short of the 28-vote threshold needed to potentially trigger minority report and a vote on the floor of the full convention next week.

Republican advocates for LGBTI rights also tried unsuccessfully to modify language that called for children to be raised by a married mother and father to read “stable, loving home” instead. However, an amendment offered by Perkins to allow for conversion therapy slipped through a subcommittee without opposition.

Republicans also softened proposed language on transgender access to bathrooms. Although the subcommittee on family issues added a provision stating: “We support and encourage the common sense practice of protecting public safety and personal safety by limiting access to restrooms, locker rooms and other similar facilities,” it was later removed in a full committee hearing. In a motion offered by the subcommittee’s co-chair, Patricia Longo of Connecticut, the language was described as duplicative and scrubbed without debate.

However, although the platform offered language saying that Obama’s executive order on the subject was “illegal, ominous and ignores privacy issues”, it added: “We salute the several states that have filed suit against it.” This didn’t address the concerns in the subcommittee that introduced the amendment, which Melody Potter of West Virginia emphasized was a safety issue, arguing: “We have to take a stand.” Instead, it represented a shift away from supporting affirmative legislation on the subject such as North Carolina’s HB2, focusing instead on opposition to the Obama executive order on the subject as overreach.

The platform also contained a provision calling internet pornography “a public health crisis”. Mary Frances Forrester, who introduced the amendment, told the Guardian: “We know how big of a problem it is. It is an insidious epidemic, and everyone knows that and that is not a controversy.” She hesitated, though, to predict whether a Trump administration would follow through on the pledge to crack down on pornography. “I don’t think there are many of us that want to predict exactly how it’s going to come about,” Forrester said.

Delegates also pushed back against efforts towards medical marijuana and drug decriminalization. A proposed amendment to encourage states to legalize cannabis oil for medical reasons was rejected as one delegate, Noel Irwin Hentschel, linked marijuana use to mass killings: “All the mass killings that are taking place – they are young boys from divorced families and they are smoking marijuana.” Other opponents linked marijuana use to the heroin epidemic.

The platform committee will finish its work on the GOP’s proposed platform on Tuesday as it deals with potentially contentious proposals about trade and immigration.