I know Peter Duesberg, the guy that started this whole conspiracy theory that Headhunter is refering to in yet another of his psychotic attacks. I met him back when I was at Berkeley, and I got to talk to him a lot about this.
His theory was concocted back in 1987, when in fact the disease was mostly in the gay/drug user community. The nearby San Francisco and Oakland are pretty fertile in both communities, and it seemed an obvious conclusion from his observations in this part of the Universe.
Of course, in the past 20 years we learnt a lot, and very few people still believe the guy.
The current consensus in the scientific community is that the Duesberg hypothesis has been refuted by the huge mass of available evidence, showing that Koch's postulates have been fulfilled by HIV, that virus numbers in the blood correlate with disease progression and that a plausible mechanism for HIV's action has been proposed.
In the 9 December, 1994 issue of Science (Vol. 266, No. 5191), Duesberg's methods and claims were evaluated and found that:
* it is abundantly evident that HIV causes disease and death in hemophiliacs (Cohen, 1994a)
* HIV fulfills Koch's postulates (Cohen, 1994b)
* the AIDS epidemic in Thailand cited by Duesberg as confirming his theories in fact is evidence tending to confirm the role of HIV in AIDS. (Cohen, 1994c)
* AZT and illicit drug use, contrary to Duesberg's claims, do not cause an immune deficiency to or similar to that seen in AIDS (Cohen, 1994d)
From what I gathered in my conversations with him, there are three basic reasons why he keeps insisting on this "theory": political beliefs, pride and self-interest.
His political beliefs, let's say... are illegal in his native Germany. That's one of the reasons he immigrated here.
Also, keeping his ground has gained him a lot of recognition, and a lot of support from fringe groups. If he caved to the mainstream thought in this area, he would no longer be relevant. He would probably be completely forgotten.