Lesbian and gay activists in the US have expressed anger over the revelation that two lesbian bloggers were in fact men posing as gay women, saying the hoaxes would make the community more suspicious of newcomers and each other.

Paula Brooks, executive editor of the US-based lesbian and gay news site LezGetReal, was exposed on Sunday as being a fake identity created by Bill Graber, who now says he is a 58-year-old from Dayton, Ohio.

The revelation came 24 hours after Tom MacMaster, a 40-year-old American PhD student at Edinburgh University, confessed that he had posed as a young lesbian woman in Damascus who had been kidnapped by Syrian security forces.

"This is really an outrage," said Judy Dlugacz, president and founder of Olivia, a travel company for lesbians. "We all need to be aware that there are people out there who will abuse the blogosphere."

Michael Triplett, who runs a blog for the National Lesbian and Gay Journalists Association, said all bloggers would lose credibility. "I think people are just going to be more suspect of people they don't know or people they don't have familiarity with," he said.

"Blogs are already being discredited as people sitting around in their pyjamas talking about news.

"Now you are talking about guys in pyjamas pretending to be women in their pyjamas it really makes it even more of a credibility concern," he said.

Speaking to the Guardian by telephone, Graber, who said he was a former air force pilot and retired construction worker, said he felt "horrible" about his four-year deception. He said he had created the fictional character of Paula Brooks, a gay woman with three children from the Washington DC area, after a lesbian couple with whom he was friends had been badly treated at an Ohio hospital.

"I wanted to run a gay and lesbian news site," said Graber on why the character had set up the LezGetReal site. "I didn't think the mainstream did a particularly good job of it, and I thought that the best way to do it was to have people who were in the life, living the life, tell the story."

Graber had given MacMaster, posing as Amina Abdullah Araf Al Omari, a Syrian-American lesbian, a space to write about Middle East issues before he went on to create the Gay Girl in Damascus blog, which was exposed this week as an elaborate hoax.

Graber told the Guardian that he had not suspected MacMaster, who via his character Amina had flirted with Brooks. "I didn't flirt. I'm all about the business," said Graber.

As doubts about the Gay Girl in Damascus blog intensified last week, following a fake post from MacMaster saying the young lesbian woman had been kidnapped by Syrian security forces, Brooks passed information that helped uncover MacMaster to a number of news organisations, including the Guardian.

Graber would tell reporters by email that Brooks was deaf, and so phone conversations had to be conducted with a man she said was her father. It was after one such conversation that the Guardian developed serious doubts over Brooks's real identity.

Further investigations established that, rather like the supposed young woman in Syria, even close associates had never met Brooks, and that her CV was fake. Challenged directly by the Guardian before MacMaster admitted to being Amina, Graber acknowledged Brooks was a fake identity but continued to insist that Brooks was a lesbian woman with children.

Asked by the Guardian, following his admission, if he had enjoyed attempting to manipulate the media investigating the Amina story, Brooks said: "What I wanted you guys to do was catch the sonofabitch. Because he was doing damage.

"He was doing damage to my site, damage to the Syrian people. Damage to gays [sic] ... [MacMaster] took this into a whole different realm of fantasy that blew up to where he was ... creating something that didn't exist. I want actual news, I don't want some fantasy."

The Gay Girl character, he said in a followup email, was a "monster" created by the media, including the Guardian.

LezGetReal operated in a small world. There are relatively few general news sites run by lesbians, and for some writers LezGetReal offered a chance to break into writing. Within those close circles, a number of people said they felt betrayed.

There was almost no sympathy for Graber's argument that the reason he had created the false identity was in support of lesbians.

"Look at how much power he wielded controlling this," Dlugacz said. "The fact that he created this illusion and that he enjoyed it so much, that he was perpetrating a hoax and had such a good time with it, that is pretty pathetic."

"There is almost something pathological about it," said Triplett, "I really don't get the idea of wanting to take on an entirely different person, especially [one in] a group that you have no affinity with."

In a statement the US embassy in Damascus said it had spent "many hours attempting to confirm blogger [Amari's] citizenship and obtain more information from friends and family that could help in efforts to locate her and provide consular assistance.

Speaking to the Guardian by phone, Melanie Nathan, a former partner in LezGetReal who was estranged from Brooks, said: "In my opinion, what Graber has done, to be a straight man calling himself a lesbian, is tantamount to impersonating an entire community."