I do hope you didn't really mean plaque but plague. And I've found no evidence of that. But it would be possible - people with sickle-cell anaemia are resistant to malaria, for instance. Let's just say that such trade-offs aren't unheard of.
As far as AIDS deniers go... while they're entitled to their opinion, doesn't mean said opinion is right. People like that are harmful at best, just like those who claim that vaccines cause autism. The problem here is probably the fact that AIDS doesn't kill you as such. People who develop AIDS die of other diseases - a simple cold can develop into deadly pneumonia, for instance. That's what the acronym stand for - acquired immune deficiency syndrome. HIV screws with your immune system to the point where it doesn't work any more, so you can't fight off even the simplest infections.
There is plenty of evidence showing that HIV infection causes AIDS and no evidence to the contrary. It's that simple. Claiming otherwise is claiming something that's contrary to reality.
AIDS deniers are especially dangerous in some third world countries, where antivirals aren't readily available, and they're lying to change the general opinion, so the country wouldn't have to spend money on importing medicine and/or are trying to promote cheaper, domestic (tribal) medicine. That kind of attitude is dangerous and is only causing HIV infection to spread (the same goes for claims that condoms don't prevent infection
or that condoms actually cause AIDS
, which were made on several occasions by different religious figures
But AIDS deniers aren't the only nutcases out there - you also have germ theory deniers. There's an interesting article on that here