I have thought for a while now that there MUST be some non-negligible degree of narcissism present, or at the very least a level of dissociation that outwardly presents as arrogant, for a transition to actually take place or even to initially demand the cognitive dissonance from others of "I am the opposite now of what I was before, ignore all sensory input and let me gaslight you"

you should work with him to get over this instead of slow roasting him over the roaring flame of your insecurities and unresolved trauma