'He could be very entertaining," Stalin's niece Kira Allilueva told the biographer Robert Service in 1998. The dictator had her jailed in his last round of purges, after World War II, but she still remembered how kind he had been to her when she was a little girl, how he took her on his knee and sang songs to her - and that he had a fine singing voice.

Not only that, but he wrote limpid poetry in Georgian as a youth, he read Dostoevsky and his subordinates saw him as a considerate boss.

He also had millions of people killed, which is why, until Service's recent book, Stalin: A Biography, people were reluctant to write about his human side.

Yet a moment's thought will tell you that the great dictators could never have achieved such power over other people if there was not something attractive about their personalities.

Maybe it's the fact that most of their victims are no longer with us that now makes it possible to see the mass murderers of the mid-20th century as complex human beings rather than one-dimensional monsters.

It will be quite a while before some brave Cambodian makes the first film that shows the human side of Pol Pot, and in China they haven't even got around yet to admitting officially that Mao Zedong was a monster. But in Europe, where the horrors are a bit more distant in time, it's all the rage.

The wave of books and films about human monsters began with a couple of groundbreaking Italian biographies that showed the human side of Benito Mussolini; but he wasn't really in the first team as a mass murderer.

Service's biography of Stalin is in a different league - and so is Bernd Eichinger's groundbreaking film on the last days of Hitler, The Downfall (Der Untergang).

Released in Germany to generally positive reviews in September, it is the first German film to tackle Hitler directly - 59 years after the man's death. Set in the last 12 days of Hitler's life as the Soviet army fought its way towards his deep, multi-storey bunker in central Berlin in April 1945, it documents his rages and his self-pity, but it also shows him as an ordinary human being.

He says "please" and "thank you". He eats pasta. He is kind to the terrified women who continue to carry out their secretarial duties as the apocalypse rages overhead.

When he finally marries his mistress Eva Braun (which he always refrained from doing because, he said, he was wedded to the German people), he is implicitly accepting that it is all over, and that they will have to die in a little while - but he kisses her gently on the lips.

It's all true, based on the accounts of people who were in the bunker and survived, but it stirred up a storm in Germany. Most of the criticisms echoed Golo Mann, one of Hitler's first biographers, who warned 30 years ago that the more biographers explored Hitler's origins and psychology, the more inclined people would be to understand him. From there, Mann said, "it is only a small step towards forgiving and then admiring". But that is not true.

Admitting that Hitler and the other great murderers were human is painful, but to deny it is to absolve ourselves of any moral connection to what happened.

Whatever the risks involved in acknowledging our common humanity, they are outweighed by the need to understand that it is human beings, not instantly recognisable as moral monsters, who commit the great atrocities.

Consider Ernesto "Che" Guevara, the revolutionary hero whose iconic image, taken from a 1960 photo, once graced millions of students' walls. There is no doubt that injustice inspired genuine rage in him. Since he never got to rule anywhere, however, his image is unsullied by any knowledge of what he would have done if he actually had power.

There has been a film out about Guevara, too. The Motorcycle Diaries follows the epic trip he and a friend made up the length of Latin America on an old Norton 500 in 1952. It documents how these young Argentine sons of privilege had their eyes opened to the realities of poverty and exploitation in Latin America - and leaves them just before Guevara joined Fidel Castro in his Mexican exile and began his meteoric revolutionary career.

Guevara comes across as an attractive human being, and his dedication to the poor is clearly genuine. But the ideology he espoused in order to change all the human sorrow he saw was Marxism, and he did not water it down.

He used to prostrate himself before portraits of Stalin, and he advocated "relentless hatred of the enemy that ... [transforms] us into effective, violent, selective and cold killing machines". If he had led a successful revolution in Bolivia, instead of dying in the attempt in 1967, there would certainly have been mass killing.

Mass murder in the name of a principle is as human as eating apple pie, borsch and steamed rice. Treating the perpetrators as space aliens simply disguises the nature of the problem. The potential mass killers live among us, as they always have. They often have perfectly good manners, and some even have high ideals. And the only way the rest of us have to keep them from power is to remember always that the end does not justify the means.

Gwynne Dyer is a London journalist.

© 2004 Dr. Gwynne Dyer

###