I have to agree. Evolution seems to have placed human empathy on a spectrum -- some have a lot of it and perform caregiver functions within a community, others have less of it and tend to perform defensive function. While we may not have physically differentiated castes as do ants, it would be unwise to assume that all healthy humans will have the same level of empathy. Layer on top of that, military training designed to further attenuate empathy, and you get a very select group. That said, since that group is basically "soldiers", the claim "Soldiers can kill without moral injury", isn't inaccurate.
> Evolution seems to have placed human empathy on a spectrum
What makes you say the spectrum is caused evolution? I would say, based on what I've seen, it's caused by lifetime experience and parenting/mentoring.
> some have a lot of it and perform caregiver functions within a community, others have less of it and tend to perform defensive function.
Experts consider empathy an essential tool of conflict: it's required to understand the emotions of the enemy, which is necessary to anticipate and understand. Remember that humans evolved without literacy and possibly they wouldn't have understood their enemy's spoken language.
> military training designed to further attenuate empathy
I would guess that it's the opposite, for the reasons above. Also, afaik empathy for others is the same mechanism as empathy for oneself and that is essential for processing emotions, which is essential for handling traumatizing experiences. People with less empathy are much less functional under stress.
