I have read quite a bit on personality disorders (as I thought I had one). my understanding is some of them are defence mechanisms that have got out of hand and become maladaptive, often as a response to bad experience and trauma, rather than an innate personality traits (though certain factors make people more predisposed).
I agree with you in regards to psychopathy though, I think all human traits will have a normal distribution and there will always be outliers, nature doesn’t make a perfect design that then goes ‘wrong’, it tries out loads of things, most turn out the same, some are rare. empathy (hate this concept because people use it to both mean being able to read people, and to care about people as if it is one thing but I mean just in the later sense here) will be like this, with some outliers.
So guess it is important to make a distinction between people that have developed anti social behaviour disorder due to psychological damage, and those that are just naturally that extreme (however, don’t think it is understood enough yet and the disorder does currently cover both). but I don’t really know what I am talking about, and like darwinbabe says, probably something we shouldn’t be talking about so hope I haven’t gone too far here