Dr. Hare's research, his books, and his Psychopathy Checklist are peer-reviewed and he is considered to be highly knowledgable about psychopathy; a leading expert in the study of psychopathy, in fact.

His reason (if I understand correctly) for studying psychopathy is that although psychopaths comprise only a small percentage of the total population, psychopaths account for an extremely high rate of criminal acts perpetrated on society.

Not just violent acts; psychopaths can be the "snakes in suits" who commit financial fraud in large corporations, or they engage in serial bigamy or "love fraud", which is seducing and marrying people just for their money, stealing them blind, then dumping them, disappearing, relocating to new "hunting grounds" seducing and robbing another victim, over and over.

(There is even a website called "Love-Fraud Blog", which gives emotional support to the victims of these serial bigamist/con artist psychopaths.)

Just to be accurate, currently, the correct or "official" diagnostic term is "antisocial pd." "Sociopath" was the earlier term used by the DSM, but that was discarded in later editions in favor of "antisocial" personality disorder.
I believe the current edition, the DSM-5, continues to use "antisocial pd".

Dr. Robert Hare and others want the term "psychopathy" to be included in future "DSM" editions, to be used to designate specifically the most extreme form, which includes both antisocial pd PLUS narcissistic pd traits.

In fact, if you read the "Hare Pyschopathy Checklist" online, one of the three sections of the checklist are the traits of narcissistic pd.

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