In Chapter 2 he states:

The ideal response to killing in war should be one similar to a mercy killing, sadness mingled with respect.
The ideal response?

Not sure about that.

What feelings should I (or the gunship crew) have when I see a video on Youtube where a gunship kills some Afghans in the process of laying an IED?

All killing is not equal.

Is killing an enemy in war the same as that of a drive-by shooting? The killings perpetrated by a deranged serial killer?

So if soldiers select another word for killing -destroy/annihilate/dispatch/eradicate/erase/neutralize/obliterate/slay/waste/wipe out/zap - it has more to do with differentiating the act of killing which they get involved on with that of criminal murderers than mask their own actions. Of course much of the motivation behind the replacement words chosen for killing has no subliminal psychological basis at all.