There are several problems which have caused what you refer to as childish comments.
1) Gates is involved. Gates is a proven corporate rogue who, while a significant section of the World's population admire him (generally those more ignorant of his history, some even thinking he invented computers), he only generates dislike and cynicism among those concerned about his history of cheating and extortion. They see his "green" and "humanitarian" activities merely as an attempt to repair his bad reputation.
2) Technology for recycling sewerage has existed for years. Gates is posing as if he were involved in a new inverntion.
3) There are some simple low-tech solutions to these problems. Water shortages tend to occur where settlements have sprung up in areas in past times where water was adequate (they would not have been settled otherwise) but it has since ceased to be, or because a past irrigation/water supply system has broken down through neglect.. A better solution might be for the people to give it up and move to a location nearer a river from which water can easily be piped (using wind pumps) and filtered much more easily than sewerage can. In fact they may already be near enough.
Plastic piping is really quite cheap, wind pumps are low-tech, and the rivers of the world currently dump vast quantities of fresh water into the sea every day. I understand that there are stacks of plastic pipes in some African villages, put there by humanitarians for making water supplies, that no-one has actually bothered to assemble. What is needed is some organisation and effort, perhaps by the villagers themselves. So what chance of maintaining Gates' apparatus?
I am probably one of those you consider unintelligent, childish etc as I have made some critical comments earlier, but keep it going because I feel very secure against that. Just to make sure here it is again :- :
Gates talks shit, sells shit, and is a shit.