I think some of these disorders are more "creepy" because the person can seem completely normal, perhaps in some cases even more engaged and perceptive than average when they're only slightly manic, and then their behaviour can change so rapidly to something completely different that your brain struggles to connect them together as the actions of the same person.

Someone who is constantly behaving in a socially unacceptable fashion is immediately thought of as a tragic case of some suffering from a serious mental disorder. Personality disorders are much more insidious and it's harder to accept that they are so different at some fundamental emotional level than ordinary people.