WikimediaI've conducted my own quasi-anthropological studies of the Occupy movement here in the UK. I doubt they will ever make it into any academic journal (I'd worry if they did) - but I've found it useful to understand the reach and capabilities of what has been a remarkably enduring, innovative and truly popular movement.

Like in the US, though many disagreed with their methods, this small group, with chapters across the world, brought the injustice of 2008 to the fore in a refreshingly bombastic manner. Polls continuously showed that large numbers of the public agreed with their political goals, though few would join them freezing on the paving slabs of the City of London or Wall Street.

I built my tentative conclusions after spending some time in the camp outside St Pauls a few years ago, in the communal squats the protesters moved to after the police dismantled that camp, and now in their latest manifestation on the green outside Parliament. I found that "Occupiers" fell, and still fall, into three categories.

Firstly, the Impressive - thoughtful activist-academics who want to generate practical ideas for a better society, however radical. Secondly, the Determined – washed-up but proud, angry and wizened, impressive dreadlocks. Eyes that betray a history of recreational drug use. The Determined battled the racist National Front in the Eighties, globalisation in the Nineties and now want to take on the banks.

But finally, you have the Naive - youngsters who thrill themselves by dressing in black, tying evocative scarfs around the lower half of their faces, and taunting policemen. In one incident a couple of weeks ago, I watched a young Occupier tap a policeman on his helmet continuously, until he was arrested and bundled towards a police van. His departure was accompanied by jealous cheers and hoots from his mates. They scampered around yelling "Pigs" and "Shame on you!" to the frustrated cops. The general naivete is betrayed by comments such as "You know mate, there's six families in the world and they basically control everything" or "Honestly, these cops are worse than Saudi Arabia. We're living in a dictatorship.”

Russell Brand, now a celebrity activist, has recently appointed himself a poster boy for the Occupy movement here in London. And while the first two categories of Occupiers are highly endearing, unfortunately Brand falls into the hopelessly naive third category. Despite being half a decade late to Occupy - in speeches and TV broadcasts he claims to be speaking the word of the people when he rails in very general terms against bankers, politicians and those ever-nasty bogeymen - corporations. It's stuff we've heard before.

A couple of weeks ago, Brand appeared on the BBC's Newsnight - before a huge blown-up graphic of Che Guevara, the controversial revolutionary's facial features replaced with Brands good looks.

He congratulated himself on the comparison, though did note that Guevara had a dark side to him. Guevara was a life-long activist, unlike Brand - though that's not to say latecomers to politics aren't welcome. But Guevara was a stallion of a thinker. He wrote thirty books in Spanish, most of which were later translated into English. Jean-Paul Sartre described him as "not only an intellectual but also the most complete human being of our age". A declassified CIA 'biographical and personality report' from 1958 begrudgingly recognised Guevara's wide ranging academic interests and intellect, describing him as "quite well read" adding that "Che is fairly intellectual for a Latino."

In contrast, Brand seems an intellectual pony. He point-blank refused to engage with a graph presented to him by Newsnight's host Evan Davis. "That's a graph mate," he screamed. "I don't care about your stupid graphs, that's what people like you use to confuse people like me!" Davis politely pointed out that the graph demonstrated one of the very points that Brand had made, that real wages were falling. Brand, sheepishly, engaged.

Wannabe Che also ranted about General Motors - saying it should be dismantled, taken away from shareholders, and its resources made to do something useful. He didn't know, as Davis pointed out, that GM is now partly owned by a trade union and also the Canadian government.

His lack of detailed knowledge was typical. In one damning review of his book in The Guardian, by centre-left columnist Nick Cohen, "His writing is atrocious: long-winded, confused and smug; filled with references to books Brand has half read and thinkers he has half understood." Likewise, when last year Brand called on young people not to vote - the punk musician Johnny Rotten called him a "b**hole," claiming "he was demanding that the youth be ignored." Others have called him 'irresponsible', 'naive', self aggrandising', 'incoherent'.

And Brand is also somewhat of a hypocrite, despite railing against corporate bogeymen and capitalism - his book is published by a tax-avoiding company, Harpers, and his film company is bankrolled by City financiers.

He speaks in generalities. His populist rhetoric is not backed with an eye for detail. His lack of political intellectualism is the mark of a demagogue showboater.

What's more - the Left don't need Brand. And this is why it is important to criticise him.

He's discrediting the Left at a time when disillusionment over wage stagnation, welfare cuts and privatisation is presenting a huge opportunity for resurgence. Even the Green Party are on the rise.

The weekly writings of Owen Jones, a Guardian columnist, are unashamedly left-wing and extraordinarily popular. His call for the trade unions to rise again would have been unpalatable ten years ago, but now the people seem ready. Even the Labour Party have, under “Red Ed” Miliband – suggested they may veer towards their left-wing roots. The passing of Bob Crowe and Tony Benn, juxtaposed with that of Margaret Thatcher – put the long-term legacy of de-unionisation and privatisation back in the public eye.

Yet Brand's pseudo-activism, which appears whimsical and opportunistic, could de-rail all this. There is nothing more important in politics than credibility. A speaker is impressive not just because of his speech, but because you know, watching him on the podium – that you could sit in the pub for hours with him afterwords and talk about his ideas. Brand has nobody convinced. And with the media so keen to cover his ramblings – he may be more trouble than he's worth.