It is a survival tactic of the victims of narcissists. Not according to Lasch and others. They will tend to use different techniques in obtaining narcissistic supply. Remote diagnosis is very unserious. They will belittle each other and exaggerate their own achievements and qualities.
Narcissists often modulate their sense of self worth by berating others.
The book came much later when I realized the pent up pain and solitude that narcissism wreaks upon its sufferers and victims. It is a pernicious condition, the root of many mental health disorders, and very poorly understood and studied. Mine was shorter. Not a big fan of TV and even less so of remote diagnosis. As I said NPD is pretty new.