For my part, I will say this; I do not accept that human morality, for the vast majority, is based on hate, envy, greed or self-interest. In fact, quite to the contrary, the basic benevolence and cooperative nature of most people is what has allowed a very small, depraved and abhorrent group to prey upon the majority of the species for millennia.
I like to think that this negative trait will eventually be eliminated by evolution, provided our species can survive long enough. That small group of deviant individuals is like a parasite within the body of humanity. They have managed to pass along whatever genetic flaw they possess through the ages. They can only survive if there is a significantly larger population of healthy, sane and basically good people to maintain them.
“You see, evolutionarily speaking, psychopaths should not exist. Throughout history it can be seen that human beings have needed to co-operate and care about one another in order to survive and produce a new generation that will carry on the processes of society. Most human dynamics are based on people trying to work out their problems and come to resolutions agreeable to the greatest number or, at the very least, in the interactions between two people. The issue of trust is paramount. Someone who betrays your trust is someone you cannot live or work with. Therefore, psychopaths, who are untrustworthy, should have long ago become extinct. But that isn't the way things are. It appears, in fact, as if psychopathy has increased!” Source
Evolutionary psychologists regard psychopathy as an inherited personality style that has evolved because glib, deceitful individuals—as a minority within a larger population of trusting folk—often reproduce with much success.” Source
Other investigators, such as neuroscientist R.J.R. Blair of the National Institute of Mental Health (NIMH) in Bethesda, Md., regard psychopathy as the result of a still-unspecified genetic disorder. The inherited defect interferes with the workings of the brain's emotion system, which is centered in the amygdala, a structure especially concerned with perceiving dangerous situations.
Some species of parasites are termed species specific. This means that they can complete their life cycle in only one species of host. Should they enter the wrong species they are unable to complete their life cycle and die, all generally without the host requiring treatment. Source
What’s nice about this explanation is that it not only explains why psychopaths exist, but also why we’re not all psychopaths. If there are few enough psychopaths in the population, then being a psychopath makes sense because you’ll mostly have winning confrontations with nice people. But if there are too many psychopaths, then the gains from taking advantage of nice people will be swamped by the losses from confronting other psychopaths. In equilibrium, you’ll get both psychos and nice folks, with each strategy generating approximately equal returns, and with the precise balance determined by the relative payoffs of different interactions. Source
There's currently a bull market in corporate psychopaths, according to psychologist Paul Babiak of HRBackOffice, an industrial-consulting firm in Hopewell Junction, N.Y. Organizations undergoing major changes, such as downsizing or mergers, provide a chaotic atmosphere that savvy psychopaths exploit", Babiak holds. "They cozy up to a firm's power brokers, manipulate coworkers, and intimidate underlings on their way up the corporate ladder, stealing everything possible along the way.
Not all psychopaths resort to violence, however. Highly intelligent people with psychopathic personalities find fertile, nonviolent opportunities in conning and manipulating others, in Porter's view. Source