Say that to Elon Musk. Imagine the inventors using this money in the same way Musk did. If they do (or at least try) I'd say humanity comes out on top - even though this killed our dream of VR in the near future.
But even if you think their motives behind the charity are selfish, don't discount the effects.
How many Einsteins, von Neumans, Ramanujans, or Musks (pick your genius of choice, really) are stillborn in the developing world because of malaria or HIV? How many never achieve their potential because of malnutrition or polio?
If the Gates Foundation eradicates malaria and polio, and we get a few more world-changing geniuses out of it, they'll have done much more to push the technological envelope than any other endeavor.