"The article does not in fact dispute that people are infected through heterosexual sex. It does state that one is more likely to acquire it through anal sex. Or needles. It suggests that the reason that AIDS infects both sexes to such an extent in Africa could be due to lesions or other infections the inhabitants have acquired there, perhaps due to the tropical climate, real poverty and primitive conditions."
The opposite could be true as well. What would a rural witch doctor say caused the purple legions? Demon possession? If purple legions were caused by tropical climate, poverty and primitive conditions, then why don't we have something like this documented as cause of death in past centuries? Also, how many people that were HIV negative were cured of their purple legions by western medicine? If there was a 'purple legion' disease, the west would know, and missionaries would know, and something would be done to cure it. There would be something in the historical record when westerners started visiting and settling in Africa.
I don't think that climate, poverty, etc. cause lesions or open sores, but those things surely contribute to them. I don't doubt that you are correct in stating that the existence of those things has been recorded by westerners.
Certainly, if not the reverse, then something other than the lesions, punctures and open sores could contribute to AIDS in Africa. Even so, it's likely that any type of open wounds aggravate the situation, since they would make infections of all types more likely. In fact, infections of all types are usually associated with AIDS, I believe.
As I said, I don't believe the authors of the article made their case regarding AIDS in Africa. Nevertheless, I tend to agree with them that politics obscure the situation to some extent.