What's to say about Africa and Aids? Except that if the pope were as omnipotent as people make out, he'd be able to make individuals subscribe to the whole package of Catholic teaching on sexuality, on fidelity within marriage and chastity, not just condoms. I've never quite been able to believe in Catholics – Africans or otherwise – who are so scrupulous that they couldn't possibly use condoms, but will resort to prostitutes.
What's to say about Africa and Aids? What indeed?
You could begin by pointing out that chastity has a very poor record as a public health policy, and is generally only proferred by simpering, sanctimonious prigs that care more about their own superstitions than the lives of actual, real, people.
According to the BBC "Aid agencies can find that their biggest challenge is trying to overcome cultural objections to using condoms."
Presumably some portion of this cultural objection is down to Catholicism, and of those Catholics who hold this view, some would change their view in response to a papal bull endorsing the use of prophylactics.
You could go on to point out that his Holiness' advocacy of such traditional Catholic alternatives to the use of condoms has failed to halt the the continued spread of HIV and Aids across the world.
His Holiness is not omnipotent, but has at his disposal the means to end a great deal of human suffering, and yet chooses not to do so.
That is what you can say about Africa and Aids.