Most media which feature a character with psychopathic personality disorder try to play up their inhuman nature as much as possible. Many decide a good way to hammer the point home is to have the character reject all forms of sexuality.
This trait is contrary to psychopathic pathology, which typically features a strong tendency for promiscuous behavior. Most likely writers Did Not Do Research
and assumed a lack of emotions also means they cannot enjoy sex and therefore would not want it...
- In Death Note Light turns down women left and right including a major supermodel. He only seems to ever date women when they're useful to his schemes.
- In the first season of Dexter, Dexter Morgan claims to find sex "undignified" and intentionally dates a rape victim in order to avoid it.
- Sherlock's Moriarty fits this trope, only showing interest in any sex to manipulate those around him
- This is possibly true of Dr. Hugo Strange in Arkham City. In patient interviews he seems particularly detached when talking about the relationships of the inmates and at one point states openly that he's never been in love