To deny someone has an illness that they have is disgusting. I am not sure who these people are (okay except some South African politicians) but they are idiots. When someone has HIV it is a death sentence in the majority of the cases. To deny this fact shows a lot about a persons character either they are ignorant or they are despicable.
I did not realize there was a thing such as AIDS denialism, it's quite obvious that AIDS is a real threat to many people. AIDS researchers need more funding so they can find a cure for AIDS and HIV both. It is sad that poor innocent children are born with it daily because of infected parents and they can do nothing about it.
In some ways, the denialism is motivated by racism and homophobia. It is also in direct opposition to scientific research. Some of it seems to be motivated by a great deal of fear of dying, fear of taking medication etc. However it is offensive to reject science and willfully ignore the suffering of thousands of people.
It's offensive to deny any disease exists, and this does happen for people with various illnesses. Especially when a disease is more of a hidden disability than one that people can see. For example, if someone is paralyzed and in a wheelchair, sane people aren't going to deny the person is disabled. But if someone has a disease where the symptoms may not be visible, it's far too common for people to question its existence altogether, or in an individual they know. And for AIDS or any other disease, this is hurtful to the people who have it.
Individuals defer in terms of what they find offensive and don't find offensive. If you rephrased the question to is it ignorant to deny. Then I say yes. As that would simply mean you are denying a tangible scientific evidence. Which would mean either you deny all of science or are selective in what you want to claim true. So it's more about ignorance than per say about offensive.
I do not think the denial of AIDS is offensive to those with AIDS. Honestly most people who do have it probably are not advertising it because of the bad rep it has with it and how embarrassing a situation like that can be. I do think we should get people to be warmer to those facing this issue though.
Thankfully AIDS denialism is a small sect of people who cling to fallacies even when it has been scientifically and medically proved that HIV is the precursor to AIDS. I do not believe AIDS patients are offended by these people and if they are, they shouldn't. I wouldn't be offended by people who aren't smart enough to come to a reasonable conclusion.