We are a menace, the first species to break nature's natural balance of each species limited to its readily available resources.
We don't need to exterminate ourselves, we only need to find a way to limit our numbers to the minimum required to enjoy our technological advances, without destroying life itself. Certainly far less than billion humans and probably well under half a billion is possible for that to be achieved, especially with robotics and automation. But only if we don't allow AI so much power that it abruptly solves the human overpopulation problem for us.
.
Each one if us has the unique privileged of conscious appreciation of our lives. We all won the most fantastic lottery by being here at all. If your parents had done things very slightly differently, by doing it on a different night, or if your mum had gone for a walk after having fun with your dad, rather than relaxing, you wouldn't be here. If a different sperm had won the swimming race, you would never have happened. If anyone was in your place in that family, it would be a different person and those thoughts that you and I are having would never have happened - at least we wouldn't be the ones having them.
Now - that said, who do you want never to have existed, to meet your amazing target of half a billion people instead of eight billion?
See what happens - first the environmentally minded want to set a ridiculous target at COP, and then someone else wants to reduce the human population to one sixteenth of what it is.
The word is Misanthropy - the business of being suspicious of, and despising the existence of human beings.
Note - I know Flecc isn't actually a reincarnation of Adolf Eichmann or Himmler. For one thing, he and they were alive at the same time, so he couldn't be, could he.
He's just having some of the same thoughts, but in a more kindly sort of way...
Of course looking at the likes of Caroline Lucas and Mad Miliband, who knows what someone else will come up with?
Edit:
I'm having a bit of fun with flecc here. It wasn't actually him that started on the idea of there being too many of us - it was me - following the obvious conclusion that since half of our emissions are from eating and breathing we need to make ourselves scarce.