Their story seems strange even after all this time. In the late 1960s and early 1970s, small posses emerged from among the most privileged young people in Europe and America and took up arms against the society their parents had built. They bombed the Pentagon, killed some of the most senior businessmen and politicians in Germany and Italy, and became icons. Then they were forgotten - until now.
Across the West, the rebels of Christmas past are back, rattling their rusty old weapons once more. In the US, one of the Weathermen, Bill Ayers, was smeared across the Presidential election after it was revealed that Barack Obama had served on the board of a charity with him. In Germany and Italy, films about the Baader-Meinhof gang and the Red Brigades have become the home-grown hits of the year. In France, there has been a row after President Sarkozy refused to deport a hunger-striking ex-Red Brigader, Marina Petrella, to Rome.
It's easy to write-off everyone who participated in these acts as purposeless psychos, a Guerrilla High mirroring Columbine High, or to see them as spoiled Oedipussies trying to strike back at Daddy. But the truth is more complex and troubling than that.
Let's start with the group that killed nobody but themselves, because they illustrate the shades of grey in this tale. Bill Ayers joined the Weathermen, he says, for one reason. His country was annihilating a peasant society 10,000 miles away, and after long peaceful protests he kept asking himself: "How can we make the decision-makers hear us if they cannot hear the screams of a little girl burned by napalm?" Ayers' memoir, Fugitive Days, asks: when you see your country murdering three million people for nothing, what should you do?
He explains: "I felt as if my whole generation had turned a corner and walked smack into a rape in progress: the victim, a stranger - small and ragged, she looked poor, she spoke no English, she held no currency. But - and this was the shock - the attacker was a man we all knew well, somebody we'd admired vaguely without ever examining the basis for that admiration."
So they bombed targets linked to the war. They gave warnings, so nobody ever died, except three of the bomb-makers themselves.
In democracies change happens by building voter coalitions, and these bombings drove the centre towards the war-hugging Richard Nixon. One of the group, Diana Oughton, returned from Vietnam and admitted: "The Vietnamese were only mildly interested in our willingness to die and much more animated about how we were going to reach out to our Republican parents, something that didn't interest us at all." These groups had their own toxic ideology, calling for Maoism. Fighting for freedom in the name of Chairman Mao is like fighting for chickens in the name of Colonel Sanders.
Yet the row about Ayers reveals there is still a distortion in our memories of the violence of that time. After condemning Obama for vaguely knowing Ayers, John McCain boasted about his "close friendship" with Henry Kissinger - and nobody noticed the dissonance. While Ayers didn't kill anybody, Kissinger played a key role in killing three million people, overwhelmingly civilians, in a bogus cause. Can it be right to damn one as a terrorist and laud the other as a great statesman?
Other groups went even further than the Weathermen. In Germany, the Baader-Meinhof gang became convinced that fascism was rising again. "This is the generation of Auschwitz! They cannot be reasoned with!" declared leader Gudrun Ensslin. They murdered former Nazi functionaries who had been absorbed into the West German state. But then - drunk on violence - they killed totally innocent people: security guards and holidaymakers. As soon as you target civilians, you have become the monster you claim to be fighting against.
Today, there is another group of wealthy young Westerners determined to bomb their own societies, motivated by hatred of Anglo-American foreign policy and their own totalitarian ideology. Jihadis are much more likely to be doctors and BMW owners than lads from council estates. As Mark Twain said, history doesn't repeat itself, but it does rhyme. Of course there are variations in the tune. You can see this in The Baader-Meinhof Complex, where the gang arrive at a Palestinian training camp and proceed to strip. "Anti-imperialism and sexual revolution go together!" they jeer at the jihadis - who consider killing them.
But while the Baader-Meinhof Gang and the jihadis illustrate vile ways of breaching the law in the name of mad ideologies, this still leaves a painful question hanging: are there different times when it is right - morally necessary, even - to break the law? I think there is just such a situation today - and a jury of 12 ordinary British people just agreed with me.
The destruction wrought by global warming makes even the destruction of Vietnam pale. The President of the Maldives just revealed he has to buy land for his people to live on since his entire country is on course to drown in my lifetime. This is one small speck in a global maelstrom. When pundits lecture environmentalists on the need to be "moderate", they fail to see that the environment is not a swing voter in Iowa. It has an independent physical reality, and it is being disastrously destabilised today.
That's why last year, six environmental activists broke into Britain's dirtiest power station in Kingsnorth and tried to stop it spewing its warming gases into the atmosphere. When they came to trial, they called the world's leading scientists to testify. The jury of ordinary people had never seen the evidence presented plainly before. They were so horrified they acquitted the activists and several pledged to join the fight themselves.
These Sixties radicals may be poking back into our consciousness today because - for all their obvious ugliness - they remind us of our own passivity. Drugged by consumerism and comfort, we respond to the great history-shaking challenges of our times by changing our light bulbs. Shorn of the Baader-madness, the Kingsnorth activists - and thousands more environmentalists who lobby and persuade - remind us it doesn't have to be this way. We do not have to stand at the edge of a climatic atrocity and wait listlessly for somebody else to act.