I've always found this a puzzling argument. He wants to spend his billions on malaria and polio, should we let him do that or should we start a committee that decides how best he should spend his money? Maybe he can do a televised competition where people go on stage and make a 1 minute pitch for him to choose one cause over another. Or maybe he can just keep doing what he's doing and solve two really big problems and then move on to something else that he wants to do when that's done.
He didn't suggest that people pour money into malaria either, really, he just suggested that they don't pour it into connectivity, and he had a really good point. But if people want to do that, then maybe we can solve malaria and polio AND get people connected at the same time!