someone in the military describing the best way to decide who to kill

Read a book by a Navy SEAL who was in Afghanistan. He said if they were wearing black Reeboks they were fighters, shoot to kill on sight.

I'm betting he was right! But Jesus, using that as a hard criteria to execute someone?!

I’ve come to realize that a significant portion of people just think other people should die and that’s fair and they’re OK with being the ones to do it.

It has always been this way. Particularly because there are people and groups who actively materially benefit from the enforced poverty/slavery and oppression of other people and groups within the social organization of our societies. The enforced poverty/slavery will never stop without sufficient and sufficiently organized, centralized, disciplined violence to overcome those who actively benefit from the enforced poverty/slavery by means of the same; and then maintaining that authority over the exploiters until their interest and strength are no more.

It's the same reason why there's never been a "peaceful bloodless decolonization." Why would the colonizer ever willingly permit that? They would be, from a standpoint of their own material interest as a societal class, complete morons to do so and make such a willing choice. Which is why (and this is historically borne out) they must be not given a choice by an organized militant anti-colonial resistance. This is also why the "authoritarianism" criticism of the doctrine and practice of revolutionary groups like Castro's revolutionaries or Lenin's Bolsheviks is laughable; the liberal peanut gallery can only have that criticism because they succeeded and survived to be criticized; having overcome the oppressors who, in the event of the revolutionaries' failure (historically borne out in how every failed revolution played out including the previous ones in those countries); would show the truth of themselves as 1000x more vicious, having honed that capability for 100x longer.

Look up any countries' "Red Terror" in history, then look up their corresponding "White Terror." You will see [wiki:NSFW images if you click on them]. Or read about any decolonization struggle. Like in Algeria, where every uprising that killed 10 Frenchmen resulted in a colonial reprisal with hundreds of butchered Algerians.

We live in a material reality with material interests which are enforced by people who will use your pacifism as a means to exploit you easier, and kill you easier if you even are seen as inconvenient or 'in the way' of those interests, let alone if you resist and struggle against them. And that argument has been happening since Marx and Engels' time in the framework of materialism; and was exactly the realm of rationale behind the policy of terror with the Jacobins before that in the French Revolution; from which many later revolutionaries took lessons and learned from the mistakes and refined within their contemporary material conditions and circumstances.