You cannot deny that it would work. If we are seriously researching (global, species wide) solutions, it has to be part of the possible solution set.

If your focus is "survival of a given individual", then I agree it's probably not a solution. But if your focus is "survival of the human species in the long term", then it very much is a part of the solution space.

No it won't, because most of the world-destroying is done by the West (especially the US) because of high-tech high-consumption with no regards to environmental externalities.

Even if you march everyone in Africa and India do death camp (and it's always Africa and India with people like this), the US is more than capable of destroying the people by itself.