When your belief system makes you stupit...

[Lamplighter]

For this individual, the root of his beliefs can't be known.
Maybe it's along the generic lines in the current thread about " must have an enemy"

But all that aside, maybe it has to due with training an army to go to war.
First, the recruits must be trained to believe there is such a thing as an enemy,
an enemy that is a threat to your "way of life", and who will kill you if you don't kill them first.
Above all else, the recruit must learn to follow orders without question.
After years of service, doing the right things and believing the right way
for both survival and career advancement, the belief systems become rigid and self-reinforcing.

Add to all that a space of time when there is no "war"
Even Roman officers knew they had to keep their armies busy.

All this is needed for those times when a nation calls upon it's military for action.

So then, retire that individual into civilian society and those belief systems go with them.
Some vets re-adjust, some can't, and some just don't.