‘[O]ne might well describe the twentieth century as the bloodiest period of utopian political experimentation the world has ever witnessed.’ 
The regimes of Stalin, Mao, Hitler and Pol Pot support the thesis that people with dangerous personality disorders, when they act together, and when the circumstances are right, can pose an existential threat to society. Each of these leaders clearly displayed traits associated with psychopathy and narcissistic and paranoid personality disorders.
These traits include the demand for complete submission on the part of subordinates, relentless paranoia, the blatant dehumanisation of opponents, narcissistic rage, tendency to extreme over-optimism verging into fantasy, reckless risk taking, and distorted decision making, including an inability to change course in the face of disaster. The thesis that each leader suffered from dangerous personality disorders is supported not only by the presence of such traits, but by the extreme nature of these traits and their rigidity over each tyrant’s lifetime.
Each of these leaders exhibited further features of note – destructive charisma, narcissistic fantasy, and narcissistic abuse of power. Charisma was an important factor in enabling each dictator to rise to power. Each gained followers through their strength of personality and their exceptional ability to use rhetoric to influence and persuade others. Each tyrant was also driven by a strong narcissistic fantasy which shaped each of their lies and the regimes they created. Pre-occupation with fantasies involving unrealistic goals is, of course, a core feature of narcissistic personality disorder. Stalin, Mao, Hitler and Pol Pot were all driven by an utterly simplistic fantasy of an idealised future – a fantasy which was characterised by a mix of extreme narcissistic, paranoid and psychopathic elements. And each of these tyrants indulged in narcissistic abuses of power. Each used power to reshape their environment to support their grandiose visions of themselves. Each used power to eliminate enemies and prevent criticism of their inflated self-image and their prized narcissistic fantasy. Several used power to eradicate a past not in keeping with their grandiose self-image via the construction of a fictitious personal history. And all used power in a way that looked like a hypocritical betrayal of their espoused ideology, but in reality was a reflection of each leaders belief that they were worthy of the exceptions they made for themselves from the hardships they imposed on others; worthy of the lavish lifestyles they led while others starved.
An explanation of the central role of people with dangerous personality disorders in political violence cannot, however, be based simply on the personalities of individual leaders. Such an explanation must include all three elements of what political scientists have called the ‘toxic triangle’ of destructive leaders, susceptible followers, and conducive environments.
In terms of susceptible followers, Stalin, Mao, Hitler and Pol Pot all rose to power not simply as isolated individuals, but as a member of a pathological group which facilitated their rise. Each of these groups – the Bolsheviks, the Chinese Communist Party, the Nazi Party and the Khmer Rouge – seized power according to the process described by Andrew Lobaczewski. The evidence suggests that not only did many of those close to each tyrant suffer from dangerous personality disorders, but that people with such disorders also played a key role, down to the village level, in securing the pathological group’s hold on power. In Stalin’s USSR, Mao’s China, Hitler’s Europe and Pol Pot’s Kampuchia, the presence of people with dangerous personality disorders in every town and village, who responded to the opportunities that the pathological group’s seizure of power presented to them, resulted, as Lobaczewski described, in the segregation of society into a psychologically disordered minority wielding power over the psychologically normal majority. People with dangerous personality disorders throughout these societies swelled the ranks of those actively participating in the destructive leader’s agenda, both because they shared the leader’s world view, and because they were presented with lucrative opportunities to ruthlessly pursue their own ambitions, regardless of the consequences for others.
This diagnosis of the catalytic role of people with dangerous personality disorders in mass political violence does not, however, allow us to escape the essential role that psychologically normal people play in acts of mass murder. The numbers of people who actively participated in the atrocities perpetrated under the regimes of Stalin, Hitler, Mao and Pol Pot are simply too large for all of them to have suffered from dangerous personality disorders. People with normal psychology did participate, in great numbers, in the atrocities committed by these regimes. An understanding of mass political violence therefore requires that we acknowledge the fact that large numbers of psychologically normal people, when the circumstances dictate, can come to enthusiastically support the inhuman actions of psychologically disordered leaders.
One of the defining features of a person with a dangerous personality disorder is that their psychology is rigidly fixed. Regardless of the environment in which they find themselves, they will respond in the same fixed paranoid, narcissistic or psychopathic manner. People with normal psychology, on the other hand, are characterised by their ability to think and act differently in different contexts. In times of peace and plenty most people tend to live with their neighbours in a spirit of community, tolerance and compromise. In times of threat and scarcity, however, many psychologically normal people can come to feel anger and hatred towards others, and can come to believe that violence and oppression are valid responses to the threats they face. Under such circumstances, psychologically normal people become more willing to accept assertive leaders and more likely to blatantly dehumanise perceived enemies. As the values of society begin to shift, the pathological group more readily attracts adherents from the ranks of the angry and excluded, those alienated from mainstream society, those who endorse anti-social values, and those disillusioned with the failure of the current political regime. When the pathological group seizes power and the use of violence and oppression becomes widespread, the mass of psychologically normal people are gradually forced to conform out of fear for their lives.
This description of the process through which society gradually becomes infected with the hatred and paranoia characteristic of psychopathy, narcissism and paranoia provides an explanation of why it is that ordinary human beings so often respond enthusiastically to the siren song of hatred? In this process, of course, context is crucial. In the cases of Stalin, Hitler, Mao and Pol Pot, the conducive environment included war and social disintegration, the presence of real and perceived threats, and an absence of checks on power.
The lesson we need to learn from the psychopaths of history is that democracy and the moral values which underpin it are the only defences we have against the barbarism which results when a minority with dangerous personality disorders seize control over society.
 Mark T. Mitchell, Michael Polanyi, ISI Books, 2006:xi
 Jerrold M. Post, Book Review: Hitler: Diagnosis of a destructive prophet, N Engl J Med 1999; 340:1691-1692