i can see where youre coming from, it was brave to show your idea in front of public scrutiny
but obvs moral grounds here stand, do the people who we exterminate have a say in if they die or not? isnt it every persons natural born right to have a say on how their life goes?
you could argue that these people dont matter anyway, poor labourers in mainland china/africa, no life as compared to ours, expendable, merely consuming resources which could be used elsewhere
but they exist nonetheless, and although we are talking about the grand scheme of things, they matter
the preservation of human life cannot be achieved through the culling of other lives
i propose we come to a compromise between the rich and poor countries of the world and try and co-exist with each other, and if it can be saved by that stage, nature as well
i realise that this is a long shot, and next to impossible due to the very nature of humans, but we should force ourselves (this would probably be the root of why this wont work) to co-exist and work together to provide a very long term solution to preserve humanity
this one of many scenarios, the OP's one would work, nuclear war could also "work"