I think that more people should be taught that fiction is not facts despite perhaps having some facts in it, rather than trying to purge or otherwise demonize fiction that's not totally true.

Example: one of my previous fandoms rather randomly created a 'all fics must show preparation for sex, otherwise it's bad and must not be read' "rule" which caused my immediate exodus from there because no matter how much you try, fiction will leave out crucial details and won't be "real" and, frankly, I don't want to read about enemas or douching or whatever in each fic. Similar case with your DID/evil alters/etc - no matter how much you try, fictional portrayals will not be equal to real and as such there's no need to try to make them real, true-to-fact portrayals.