They're an actual victim, but they haven't realized it yet.

They genuinely believe that these things that are torturous to experience are "normal," and they've internalized the abuse they've received that these things are normal so hard that they're offended other people are commisserating over how awful these experiences are, because it implies that they themselves are also not "normal."

Pity them. They're white-knuckling their symptoms and can't even enjoy commisserating with others.