If great efforts are made to eradicate diseases in an area that has historically been subjected to various diseases such that the local population has adopted the reproduction strategy of having large amounts of offspring to counter premature deaths, but upon eradication/reduction of said diseases there is significant delay in the abatement of the overproduction strategy if it abates at all http://www.unz.com/isteve/the-worlds-most-important-graph/
if this population surge then expands beyond it's historical borders and causes mass societal disruption on a neighboring continent whose civilization has historically contributed great innovation and wealth to the world at large, and subsequently, said wealth and innovation contribution declines because of said societal disruption, do those who sought to eradicate the various diseases harbor some responsibility for the diminished prospects of the world at large?
Granted these are delicate questions but I believe their being asked has not just validity, but importance.
Certainly, simply ignoring pain, disease, and suffering is almost universally unpalatable.
But modifying one aspect of a complex system for what appears to be perfectly benevolent reasons, it is not at all surprising to find there could be downstream negative effects, negative enough to far outweigh whatever beneficent contribution you thought you were initially making. How do you make value judgments in such cases?
Gates himself has said it is far better to help people where they are regarding the recent unauthorized population influx events in Europe.
So I don't believe he is entirely blind to these potential downstream catastrophic effects.