As an anlogy, consider how hard it would be to convince a random person they have to take diabetes medication if they don't have it. It is the same way convincing a schizophrenic person with anosognosia to take antipsychotic medication.
You seriously think the public stigma is one of the "worst" things about it? Almost no one my brother encounters knows about his diagnosis and yet he suffers a lot. I sort of doubt other people's opinions are of primary significance in that, although perhaps his perception of how others see him does seem a bit problem
If an employer doesn't want to hire someone who occasionally disappears I understand that and I'm not sure it's stigma.
Anyhow, this is a sensitive topic and thanks for discussing it. It's hard to unfurl and investigate these things. Good luck with your own experience.
Good luck with your brother.