I trust doctors to not be having creepy thoughts or actions because that's part of the act of doctoring.
Well, that's what it's really all about, isn't it? I trust J'onn to be in my head and not to doing creepy shit with my brain, because he's a hero and that's part of his hero shtick. Dr Psycho, on the other hand, is significantly more horrifying to me than Dr Light or the Joker, because oh my God get the fuck out of my head.