Exceptionalism calls specific what is not. My utterly unpublishable example is Cadjin(e) exceptionalism.
“We are the only ones ever shamed for speaking our language.” (Uninformed)
“Our experience can only be understood from the inside.” (So it cannot be an object of study, only a subject of storytelling.)
“This is a folkway only we have.” (Uninformed)
Cultural exceptionalism attempts to maintain isolation so as to remain unaware of anything that might suggest non-uniqueness.
It is also nostalgic — the Cadjin(e)s, for example, who sport the Imperial fleur-de-lys as a sign of solidarity and cultural identity, are nostalgic for the empire that (r)ejected them. This last point, of course, could bear discussion, since the fleur-de-lys is deployed as a symbol of resistance against English imperialism, but still…