And the moment anyone got wind of an attempt to try to do such a thing, enough humans would go to ground you’d never actually succeed. Hell, enough are probably already under ground for whatever reason you’d never succeed even if you did manage to catch the whole world by surprise and somehow actually release it all at scale.
The Nazi’s did not fail because they failed to try to kill humans at scale. Frankly, they did it at the largest scale since probably Ghenghis Khan. Certainly in a far more industrial fashion.
The issue is that it’s actually really hard to kill a lot of humans. Something that personally warms the cockles of my very human heart.
Embrace your ancestry of murderous (and loving) hominids, and aim to use it to make things better. Rejecting it is a false path.
I said good luck exterminating humans.
Hell, not that long ago the most technologically advanced society of the time (Nazi Germany) with a massive and state of the art army tried to exterminate a subset of humans (Jews, Homosexuals, Roma) using massive force, the latest technology, and with a near single minded focus.
And while they did kill a lot of people and perpetrate terrible crimes, they also failed rather completely at the task. Even in areas where they were literally burning everything to the ground.
What makes you think they would have been more successful if they’d also been trying to kill themselves at the same time? Hence impeding their abilities?
And humans are, near as we can tell, the most lethal animals on the planet overall.
Humans survive implausibly terrible situations on the regular, and are currently living in every major ecological niche in the environment except perhaps the very deepest parts of the ocean. Though if we count military submersibles and oil rig diving bells, they too are ‘occupied’.
Would lots of people die, and would it be terrible if an environmental catastrophe occurred? You bet. But killing all humans is even less plausible than killing all ticks, or all roaches. Humans, the most lethal species on the planet, keeps trying and failing to do so.
Short of melting the mantle underneath us anyway. We do have some folks living in a space station. Probably not enough though.