somat,

the part about narcissists and insecurity bugged me because it was almost like we failed to see the insecurity because that would be seeing narcissists as human. but this is why narcissists so quickly explode when someone confronts their inflated sense of self worth. if they were secure, they would not be triggered.

Their explosions are not about a lack of security per say, they are about sheer bloody indignation.
Take my N sister if I disagree with her she with explode she is confident, a bully, a control freak, very driven, highly materialistic and the bossiest person you will ever meet. There is NO WAY you could view her as 'insecure'. She simply does not care about anyone but herself.
She has been like this since the get go.
With her inability to feel empathy, her greed and grandiosity she will not tolerate dissension, she is 'special' how DARE YOU challenge a God like that!

The illogical idea narcissists are all like it because they are 'insecure' is Freud's theory of over 100 years ago!!
People used to believe the Earth was flat, things change as science and knowledge moves on. Now we have brains scans which can chart brain activity.
Narcissists are human, and humans as a species are highly destructive to each other, and, to other species probably because there are many narcs around.

Normal people can be confident, or insecure.
Narcissists can be confident, or insecure, they can be overt or covert, shy or loud. The issue with narcs is whatever their persona they, cannot feel empathy
IMO wired differently, a difference in their amygdala seems likely.

"Emotions
The amygdala is part of the limbic system of the brain, which is involved with emotions and other reactions to stimuli. The amygdala is a processing center that is hooked up to receive incoming messages from our senses and our internal organs. It is highly involved with different emotional responses."

http://study.com/academy/lesson/amygdala-role-in-emotion-function-lesson-quiz.html