Maybe he assumes his partner is positive, also. Maybe he feels his partner should look out for him or herself. Maybe he doesn't care.
At the very least, unprotected sex is risky in this age of syphilis outbreaks and other ever-present sexually transmitted diseases. Those diseases are potentially more threatening to HIV-positive people than they are to those who are not infected with HIV. Then there is the theoretical danger of re-infection with a new and possibly more virulent strain of HIV.
Why then is anybody -- HIV-positive or HIV-negative -- engaging in unprotected, "bareback" sex?
The West Hollywood psychiatrist, who counts many HIV-positive men and sexual compulsives among his patients, says honesty is as scarce as bright light in sex clubs and bathhouses.
"I have the good fortune to be in a private situation where people are assured of confidentiality and they tell me the truth," says Fishback. "The majority of my patients say they're not telling the truth about their HIV status. Or they are telling the truth and engaging in unsafe sex anyway.
"There's no one reason. Someone could be irresponsible, someone could be sociopathic and not care about anybody. Someone could be going through a phase where they're really angry, and it's misdirected anger at a stranger."
The tall, youthful doctor looks away and shakes his head slowly, as he talks about cases close to his heart. "I have a friend in New York who's been with his lover for 12 years. He still hasn't told him he's positive. It blows my mind."
"I have patients who have an open relationship, or maybe one is cheating on the other, and they're not talking about it, they're not being tested, they don't want to talk about it. They're in complete denial."
Twenty-seven of those who responded feel safe sex is the responsibility of both partners, regardless of HIV status. Three feel the HIV-positive partner is primarily responsible for safe sex and disclosure.
Dan Nickerson follows a "do ask, do tell" policy.
"Personally, I came to the conclusion I should disclose," he says, "and if they ask me, 'are you HIV positive?' I would tell them. I certainly wouldn't lie."
Nickerson, a supervisor of Case Management Services at AIDS Project Los Angeles, calls himself "an older guy -- past 40." Those years have given him a keen understanding of human nature. He knows the price of disclosure, but feels the price of dishonesty and denial is far higher.
"There's a lot of stigma attached to this infection, and that's very real," says Nickerson, HIV positive for more than a decade. "It's hurtful on some level. But people will interact with you differently if they think you're negative. They'll take more chances."
"I think that's fucked up," she says. "There's all this complacency, but you have to protect yourself. That's the bottom line."
Like Nickerson, Armstrong is up-front about her HIV status, especially with potential sexual partners. For both, those are personal policies that will ultimately help slow the spread of HIV infection. What's alarming is that, by all indications, Dan and Rebekka may not be in the majority.
Author Ron Mackovich thanks Jeff Bailey of posimages.com, for conducting the survey cited in this article.