By Maggie Haberman – The New York Times.

WASHINGTON — When President Trump was a candidate, he pledged his support for lesbian, gay, bisexual, transgender and queer people immediately after the mass shooting last summer at the Pulse nightclub in Orlando, Fla.

“They have been through something that nobody could ever experience,” Mr. Trump said at an event in Manchester, N.H., on June 13, 2016, delivering a hastily drafted speech that was originally intended to be about Hillary Clinton.

“Ask yourself who is really the friend of women and the L.G.B.T. community, Donald Trump with actions or Hillary Clinton with her words?” he said. “I will tell you who the better friend is, and someday I believe that will be proven out, big-league.”

Such proof did not come on Wednesday. But the president’s words were repeated with anger and frustration by a number of gay rights advocates who were angered by Mr. Trump’s abrupt decision to bar transgender people from any military job.

“We’re seeing the president’s true colors,” said Chad Griffin, president of the Human Rights Campaign. “This is who he is.”

The new ban, which Mr. Trump announced on Twitter, startling some of his aides, was at odds with the speech he gave in New Hampshire. The day before, in Orlando, Omar Mateen, a security guard, had killed 49 people and wounded 58 in the name of the Islamic State. That Mr. Mateen was a Muslim and had targeted gay and lesbian clubgoers sent shock waves through two American minority communities that have been marginalized in the United States.

“This is a very dark moment in America’s history,” Mr. Trump said that day. “A radical Islamic terrorist targeted the nightclub, not only because he wanted to kill Americans, but in order to execute gay and lesbian citizens because of their sexual orientation.”

During his speech at the Republican National Convention the next month, Mr. Trump again recalled the Pulse shooting. He reveled in applause after saying, “I will do everything in my power to protect our L.G.T.B.Q. citizens from the violence and oppression of a hateful foreign ideology.”

“Believe me,” Mr. Trump said during that July 21, 2016, speech. “And I have to say, as a Republican, it is so nice to hear you cheering for what I just said. Thank you.”

On Wednesday, the president’s supporters maintained that his response then spoke to terrorism — a stark contrast from current concerns about military preparedness.

Christopher R. Barron, one of the founders of the Republican gay rights group GOProud, which helped give rise to Mr. Trump’s political career by hosting him at the Conservative Political Action Conference in 2011, gave the president the benefit of the doubt.

“I defer to the military leaders to determine what policies around the question of trans service best allow them to win the war on radical anti-L.G.B.T. Islamic extremism,” Mr. Barron wrote on Twitter.

As a developer in New York, Mr. Trump spent his life in a city with a large gay population. Before his entry to politics, he was open to gay civil unions, and he was known in Palm Beach, Fla., where he owns the Mar-a-Lago resort, as the first private club owner to admit an openly gay couple as members.

Since his election, he has remained against gay marriage, the frontier on which the L.G.B.T. fight was waged over the last decade. Mr. Trump’s closest aides say he has never been a social crusader on gay rights issues.

But in his first interview as president, Mr. Trump suggested that the June 2015 Supreme Court ruling that legalized gay marriage should remain the law of the land. Early in his presidency, he declined to roll back some of President Barack Obama’s protections for L.G.B.T. people. But Mr. Trump has since ordered that some of those protections be dropped, including through moves that were said to bolster religious liberties but that critics feared would legally foster discrimination against gay Americans.

“I think people were hoping against hope that while he was very unpredictable, that he would be a man of his word and that also he would not want to go against the prevailing social norms that we’re used to in New York,” said Richard Socarides, a prominent gay activist and Democrat who used to advise President Bill Clinton.

“People thought, this is a guy who knows gay people, who has gay people around him,” said Mr. Socarides, before expressing a broader concern: “If this is allowed to work, he’ll go after gay marriage next.”

Mr. Griffin said that hopes that Mr. Trump had a durable connection to the L.G.T.B.Q. community evaporated during the campaign, with his selection of Mike Pence as his running mate.

Mr. Pence is an evangelical conservative who has strongly opposed a number of gay rights initiatives.

Mr. Griffin pointed to other transgender protections that had been undone under Mr. Trump. And he wondered aloud about Mr. Trump’s daughter Ivanka and his son-in-law, Jared Kushner, who know a number of gay people in their social circles in New York.

“Where’s Jared?” Mr. Griffin said. “Where’s Ivanka?”