I think a lot of people are making up their own definitions of sociopath/psychopath/ASPD...
why don't we stick to the DSM def?
Well, if we did that, we'd have to stop using 'sociopath' and 'psychpath,' since the DSM-IVtr doesn't actually use or recognize those as diagnoses. Nor does the ICD. Or the American Psychological Association. Antisocial Personality Disorder (APD... ASD is Autism Spectrum Disorder)
can closely resemeble the chronic, immoral/criminal behaviour that are popularly recognized as being 'psycho/sociopathic,' but then again, so is Dissocial Personality Disorder, Histrionic PD, and others that got listed. These are all distinct disorders, with different criteria and symptoms, so I'm not really convinced of the "sociopathy/psychopathy = APD" line that some people draw. For example, we'd all call Hannibal Lector a psychopath, but in the DSM-IV, I'd argue for a Dissocial PD diagnosis rather than APD.
The DSM understands 'impulsivity' and the otehr criteria as things that are actually causing distress to the client. So, if someone impulsively decides to head to St. Lucia for the week, and there's no negative consequence (has enough money to support himself there and back, jobs aren't lost, people don't put out a missing persons report, that sort of thing), then it can't really be used as a criteria. If, however, you fly to st. lucia with only $10 in your pocket, you lose your job as a result of the impulse, that sort of thing... Then yeah, that's a criteria that needs to be discussed.
As far as whether people with APD/DPD can be treated, it's goign to depend on your therapist and where he/she are coming from. Personally, I'd argue that cognitive behavioural therapy is a good way of allowign the APD/DPD patient to understand and be self-aware of destructive thought patterns that lead to outcomes that are socially unacceptable, or to reroute the antisocial/dissocial thoughts into an area that is more socially acceptable. In essence, this is what Dexter's "Code" does; it reroutes the thinking pattern into behaviour that is more socially acceptable.