Natural selection is survival of the fittest. As in, most capable to adapt to the environment.
Even if he spread aids to 50% of the 600 women he slept with, leading to their and their children's death, it still leaves 300 healthy pregnancies.
Even if 50% of the remaining women decided to go for interruption, it still leaves 150 children born.
Even if 50% of the remaining born children die of starvation, because the single mothers can't take care of them, it still leaves 75 adults.
Even if 50% of the children that reach adulthood are sterile because of malnutrition, it still leaves 37 viable offspring.
The nature does not care you die of AIDS. It only cares if you produce viable offspring. He still had more viable offspring than all the posters in this thread will ever have, combined.
This guy, adapted to his environment and won this round of natural selection.