Oh, CRO PCs can War Crime all day long as long as they're variations on the same moral compromise.  Once you've killed a guy, the next one comes much easier.  You've already deceived your kid, what's one more little white lie?  The second pre-midday cocktail doesn't take nearly the same level of self-justification as the first.  That's why every particular compromise only has one checkbox.

It's the steady expansion of compromise, facing new brinks and choosing CYCLOPS over basic humanity time and again, that breaks down a CRO. "I've killed, a hundred times, but can I really MURDER this guy who doesn't even know I'm in the room?"  "Sure, I've assassinated a guy, but can I really ruin someone's life and leave them, broken, in the wreckage?  That feels so much worse..." "Kill or be killed, I get it.  I even basically killed that guy last week, convincing his family he ran away with the maid and leaving him with broken legs on that Tijuana beach, but can I leave Kerry behind?  Where those cultists are going to get him?  We're battle brothers, surely I can't.... but it's rescue him or complete the mission...."  Being a monster in a specific way doesn't make the CRO (mechanically) irredeemable, it's the manifested willingness to be a monster in any way necessary that does.

The rules are ~kind of~ built on my understanding of cult indoctrination techniques.  Force a small compromise, then repeat it until they'll make it without consideration.  Leverage that guilt into compliance on a slightly larger thing.  Repeat that type of self-debasement "for the cause" until it too is automatic.  Rinse, wash, repeat.  That's why saying "I've killed once and I'll never do it again!" and "I've eliminated whole battalions of my enemies and bathed in their blood, but I'll never take another life!" have the same mechanical cost - both are assertions that the PC is reclaiming a particular moral line in the sand.