The base of most personality disorders is a defense mechanism. NPD is someone manifesting a big ego because they're coping with true feelings of insecurity in most cases. (Atypical you're much different than someone with NPD in my eyes based on all I've seen from you in your posts) What makes it so difficult to be seen is that, as the name states, it's a personality disorder. It's not just a trait; this manufactured ego is generally who they believe they are. One of the reasons NPD is so hard to treat is because the majority of people with NPD do not have the self awareness and objective perspective to see the underlying insecurity.

Someone with an ego they created without the knowledge it's not how they really feel? Well, an insult is going to get them fighting their subconscious and you'll be the scapegoat.