Psychopathy is generally-understood to have a negative effect on society overall: so can psychopaths therefore be classified as an "evil" influence on society?
I wrote earlier about how psychopathy usually results in sadistic behaviour towards society; and how some (atheistic) political ideologies and fundamentalist religious ideas can be placed into different expressions of sadism, and therefore may be seen as attempts to organise psychopathic behaviour into a social order. The leaders of such political ideologies and fundamentalist religions are therefore inevitably psychopaths (or at least display a high degree of psychopathy); hence their position.
The relationship between psychopathy and "evil" is explained in the excellent article here. In other words, much of the "evil" seen in society may well be attributable to psychopathy, especially when it is clear that a disproportionate number of them gain positions of power.
All that being said, there is also a scientific argument pointing out that psychopathy is a naturally-occurring aspect of the human condition and natural evolution. As I mentioned in an earlier article, psychopathy can be seen as belonging to a small "predator" segment of human society, one that has evolved from the nomadic, hunter-gatherer societies of pre-history, adapted to "civil" societies that were settled and less war-like, and learned to prosper in the quasi-Capitalist societies that flourished in Europe around the time of the renaissance. The industrial revolution and European Imperialism would have created even richer social conditions for the psychopaths in human society to exploit.
In this environment, psychopaths would have more easily "risen to the top": being amoral and sexually-promiscuous, this would have created the conditions for a potential proliferation of psychopathy, given the right conditions. As psychopaths are hard-wired to thrive in anarchic and fast-changing environments (that "normal" humans struggle in), this therefore gives an alternative explanation to the human factors that led to the wars of the 20th century and the rise of modern-day Globalisation.
Psychopathy therefore gives a fresh angle on the theory of "creative destruction", popular with right-wing Capitalists. Creating chaos is one of a psychopath's modus operandi; but also much of human progress has been due to out-of-the-box thinking and independent thought, which is another of a psychopath's attributes. Because psychopaths' thought patterns are different from an ordinary person, it means they can be capable of thinking about a problem in a more flexible way; because the fear-generating part of their brain doesn't properly work, they can execute their will without being concerned about the consequences; and because they are not prone to accepting responsibility, mistakes will be apportioned to someone else or a factor out of their control, leaving them free to continue.
In this way, psychopaths are fearless in experimenting with ideas: if put in a position of power, they can put their trial-and-error methodology into practice on human society. A psychopathic CEO of a pharmaceutical company can therefore try out a potentially-dangerous untested drug on thousands of people without a flicker of conscience, and if they all die, shrug his shoulders and move on; a psychopathic national leader can do the same with thousands of his own citizens, and their deaths can be called a "necessary national sacrifice".
If a psychopath therefore has the intelligence to not be caught by the authorities, and the self-discipline not to let his narcissism, indolence, spontaneity, proneness to boredom, and sadism over-power him, then he has the potential to rise to the top of society. This explains why so many psychopaths are at the pinnacle of the social ladder, hidden, or "socially-adapted" so that their condition is channeled into a suitable career outlet (such as the military, or position of social and moral authority).
If amorality is considered the equivalent of "evil", then psychopaths are, by definition, evil; perhaps even the "highest" form of evil.
But if that is true, then it raises the question of the social "necessity" of evil; that for a society to understand the difference between "good" and "evil", "evil" has to, by nature, exist to some degree. If it were, in theory, possible to identify and cure psychopathy from human society, what would the result be?
As human evolution has indicated, psychopathy exists in society as a natural human adaptation. Psychopaths may be "evil", but they have probably also been responsible for much human progress; being humanity's natural entrepreneurs, and making fearless decisions when others have been too confounded by moral confusion to do so.
Psychopaths are therefore a human "necessary evil"; a moral trade-off as, for example, when societies willingly surrender their collective freedoms to a single charismatic leader at "times of crisis". Adolf Hitler is an obvious example; Joseph Stalin is another (though both psychopathic sadists, their sadism showed different attributes, as explained here).
It would be therefore counter-productive to human evolution to try and eradicate the "evil" of psychopathy; worse, it would be far more likely that a number of opportune psychopaths would try to take control of such an operation, leaving society with perhaps fewer psychopaths, but with disproportionately more of them in positions of moral authority.
Such a result would bring human society closer to a closed hierarchy like during medieval times; quite literally a step back into The Dark Ages.