I'm not so much scared of "go kill these people". More of "stop feeding them, we need to repurpose arable land for energy production" at a point where we won't have the know how to produce food for everyone by hand, or similar scenarios.

It may still be people at the helm at the time it happens, it doesn't matter. Humans are capable of large scale atrocities, provided they de-humanize their victims. Many people in the .01% have utter contempt for poorer folks, for example.