The classification of Julian Assange as a terrorist by indignant Americans has been shrugged off here as overheated, yet I wonder if Assange is actually flattered. He is, after all, a revolutionary. I had him down as one of us – a muck-raking journalist, only with the advantage of understanding computers. But all the stuff about a new world order and history turning on its axis makes me nervous. His seems to be the only moral authority that he is prepared to recognise. During his swaggering on-line Guardian forum, he swatted away a British diplomat, who described how Bosnian atrocities were averted through secret negotiations, with a smirking one-liner: "If you trim the vast editorial question to the singular question actually asked, I would be happy to give it my attention."

Assange has clearly viewed his cyber war against American power as an on-line version of the Bourne movies; the wits and courage of one man pitted against the sinister establishment. He seeks nothing less than cyber martyrdom.

There is a reason that teachers worry about children spending all their time on-line. It can trigger a form of psychosis. Too much isolation can lead to detachment, obsession, paranoia. Julian Assange has a particular sort of fearlessness and charisma, but nobody could call him well-balanced. And what of Bradley Manning, the army intelligence analyst who passed on 250,000 classified documents to WikiLeaks? This is a young man discharged from the military for "adjustment disorder".

The transcript of his on-line chat with the former hacker Adrian Lamo – who passed on the conversation to the FBI, and, this being the new world, to wired.com – is best left to psychiatrists.

"I've been isolated so long," says Manning. "I just want to be nice and live a normal life... no one took any notice of me.... I was never noticed, regularly ignored, except when I had something essential, then it was 'bring me coffee, then sweep the floor'."

Assange did not ignore Manning. He made him feel important and righteous. Soon Manning was proclaiming that he no longer believed in "good guys versus bad guys". Instead, he had found a dazzling new ideology, which is that Information Should Be Free. And Manning had the means. There is an oddly masturbatory passage in which he describes how he triumphed: "Weak servers, weak logging, weak physical security, inattentive signal analysis – a perfect storm."

In thrillers such as 24 the computer analysts are the weird ones, brilliant but without any other developed faculties. They can be loyal like Chloe, or villains. They have remarkable power, because nobody else understands what they are doing, but are aggrieved, because nobody particularly wants to. The psychological premise of The Social Network was that Mark Zuckerberg built a billion-dollar empire on a grievance. The cool social groups rejected him so he created his own world.

There is a chip of Zuckerberg in Bradley Manning. He is thrilled by the scale of his own actions: "Possibly the largest data spillage in American history." And he is fascinatingly uninterested in money. As he says "I could have sold to Russia or China, and made bank."

He also has a distorted notion of the world. He lumps together all governments as equally bad and believes only in the shining new democracy of the internet. If WikiLeaks had revealed shocking corruption or disgraceful double dealing in the West, one would have been grateful. But is Manning, as Assange claims, "an unparalleled hero" for dumping on America? Would he be happier working for the Chinese? They are, after all, the masters of cyber intelligence.

Sarah Sands is deputy editor of the 'London Evening Standard'