Bill Gates is funding some humanitarian ventures without thinking to the next decades externalities it has. 100% feel good and PR actions, yet questionable in the grand scheme of things.
One externality I have seen mentioned goes as follows: fewer childhood malaria deaths in sub-Saharan Africa mean more unemployed or under-employed young men being tempted to cross the Mediterranean, exacerbating political tensions in North Africa and Europe. But obviously, if you are a philanthropist and saving every human life is your chief concern, then such thinking can seem repugnant.