I haven't seen Criminal Minds so I'm not approaching that. I think Split was a dangerous and reactionary movie exhausting the same old tired "scary mentally ill serial killer" trope that's been used to justify the abuse of mentally ill people for who knows how long. I don't have Dissociative Identity Disorder but I know people who do, and none of their alters (short for alternate personalities) have killed anyone. I'm sure alters like that exist because the world is a diverse place and all sorts of people exist, but when it's the public image of DID and the first thing that comes to a layman's mind, that's a problem.

I think the solution is to bring more positive representations of mentally ill people into the media so that people see them for what they are (regular people with brains that work differently). It's sad that I can't think of any examples off the top of my head, but basically mentally ill characters that aren't evil villains and have complex feelings and identities outside their mental illness while also having their mental illness as a core part of their identity (because for many people it is)