I don't understand the reasoning the APA used to justify getting rid of the psychopathy diagnosis. It seems to be quite a distinct subgroup within ASPD.

If that were the case, the solution would be easy: recognize psychopathy as a subgroup. They could call it Antisocial Personality Disorder, malignant variety, perhaps.

But the classic Cleckley psychopath often isn't an anti-social personality. Antisocial personality is based on concrete diagnostic criteria that high-functioning, intelligent psychopaths don't necessarily manifest; they may be political leaders, attorneys, judges, businessmen, anywhere arbitrary power can be found. I think they are probably better conceived as a subset of Narcissistic Personality Disorder. But the psychiatrists who pioneered in applying that diagnosis, the psychoanalyst Kohut and colleagues, have a more romantic understanding of their narcissistic patients. Politics figure large in the diagnostic manual's catalog.