As always, you are the very voice of reason. It is sad that denial is so commonly in conflict with reason.
Given that all the duplicity and denial you discuss in this essay is very real, I recommend leading with your best, that which no parent, nor prospective mercenary, might so easily deny.
"“More veterans succumbed to suicide than were killed in Iraq.”
"https://en.wikipedia.org/wiki/United_States_military_veteran_suicide"
"And here is the part that pro-military people really don’t want to hear, or don’t want to think about: many of those suicides are not because those soldiers saw horrible things, but because they did horrible things."
None of the propaganda they have been sold will cause them to ignore this particular facet of jingoism, and the consequences of 'service'. The fact that it is what they DO, and not what they see, that causes them to despair of life and commit suicide more often than they are killed in action, has no counter in the propaganda.
Lead with that, and let the rest sink in after they accept that first.
Or even lead with that, and let them tell YOU about the rest, as they realize it themselves. It is often best to lead a horse to water and let it drink when it is thirsty, rather than trying to force water down it's neck.
Even a thirsty horse will resist being forced to drink.
Thanks!