Well to be fair, he is not wrong.
We feel bad about it because we are seeing it through the eyes of MC and FMC but from an objective stand point, he's not doing something bad revealing the story.
She's using Sora's image to make herself feel better through the delusion that everyone should see...
Damn i dont know why i kept reading this the writing is terrible no one seems like someone let alone "real", they're all exasperating in their own way...
To my knowledge its more close to a BDP (Borderline personality disorder). Even Yami's background is typical of ppl who suffer from this disorder. Not saying thats an excuse but its a cool detail showing that she "knows" that what she's doing is f**ked up but cant stop herself. Its character...