Bob Geldof has joined the forces of pessimism

If they want to know how Hitler might have seen the euro, they can ask the BNP, with whom they will be sharing a platform

Like every other semi-sentient inhabitant of the globe, I regard Sir Bob Geldof as a proper saint. Like Jesus with an Irish accent. So I was depressed to discover this week that he is to expend some of that sacred capital on a cause as tawdry and parochial as the "No to the euro" campaign. It's as though Gandhi had taken up the fight against road humps. There's a long march from "feed the world" to "keep the pound".

Worse, Lord David Owen, has just said that he will not, after all, be leading the "No" fight, because it should be headed – not by someone with his intense dynamism, charisma and successful record – but by someone "outside politics". There's a definition of populism for you. The most intensely political campaign for a quarter of a century, and it should be led by someone who is not political. What kind of con is that?

It is, of course, Mr George Eustice's con. Mr Eustice, director of the No organisation, is master-minding a Poujadist strategy, with no little skill. This week, for about the fourth time, he has managed to get substantial media coverage for the same cinema ad – an ad that hasn't even appeared yet. This is a re-presentational record that even Gordon Brown at his most cunning has never managed. And it is one of these ads that features Geldof.

Given the anti-elected-politician populism of Dr No's campaign, it is ironic that the commercial apparently features the actor Rik Mayall dressed up as Hitler – the ultimate anti-politician – and declaiming: "Ein Volk, Ein Reich, Ein Euro!" You wonder how cinema visitors from euroland countries (France and the Netherlands, say) whose parents probably shared an experience of German nationalism, will react to this bizarre and unintelligent caricature. If Rik wants to know how Hitler might have seen the euro, he has only to ask Nick Griffin of the BNP, with whom he will (albeit unwillingly) be sharing a campaign. Or that staunch No-ite, Jean-Marie Le Pen.

I see Sir Bob's actions as yet another victory for pessimism. I am not saying by this that there isn't a perfectly good case to be made for staying out of the euro (though I think I disagree with it), but to make your stand over this issue is a strangely negative thing to do. The focus of the campaign, for instance, is wholly negative. Its thrust so far is that we should eschew the euro because Europe has higher unemployment, is in a mess over its pensions (which, of course, we are not) and is, in general, somehow culturally alien. Including, presumably, Sir Bob's native Ireland.

Sir Bob will, if he takes the job, find himself at the head of a broad and weird coalition. Forget the fascists, on the inside right there will be the Murdochs and the pro-monarchists, the protectionists, xenophobes, fox-hunters and nostalgists. On the left will congregate the Bennites, the anti-globalisers, the world socialists and the Green localists. In Europe the Greens may see the euro as progressive, but the British Greens alone know the truth. They want ""communities and local governments to take control of their own economies and enable them to rebuild stability". So actually they don't even favour the pound, but would like to see the introduction of the Peterborough crown and the Glastonbury groat.

Like the author, Charlie Leadbeater, I am beginning to see this less as a political division, and more as a psychological one. Why do we so often find the forces of both left and right arrayed on the same side against modernity? Because, essentially, they are pessimists. And, as Leadbeater says at the beginning of his new book, Up the Down Escalator: Why the Global Pessimists are Wrong, at the moment "pessimism is in power". It may not be in government, but the pessimists have established a kind of cultural hegemony. Theirs are the strongest voices.

At the heart of this divergence, says Leadbeater, is the question of how you see a changing world. An optimist surveys the changes since 1945 and points to longevity, improved health, greater personal choice and control, enhanced mobility, heightened self-confidence, higher rates of literacy, more diversity and more opportunity. We can choose who we love, where we live, what we watch, listen to and read, in ways that, just 50 years ago, were almost unimaginable.

The same world, however, may be interpreted as a series of losses. We are suffering, say the pessimists, loss of community, loss of identity, loss of certainty, loss of security, loss of culture, loss of spirituality, loss of morality. We wander now, rootless and materialistic, unhappy and wasteful, through a world which – every day – is getting worse. Only one thing is good. The past. In which our forefathers lived as fulfilled craftspersons in close-knit communities of happy families. The past before it was sold by greedy capitalists or betrayed by cosmopolitan elites. Pessimists now dominate scientific and cultural debates – their scares lead parents to junk a perfectly good vaccination programme because they don't trust the establishment. They lead to the complete trashing of GM crop experiments, despite the absence of any evidence that GM food will damage human health. And they also possess a remarkable shared suspicion of most supra-national efforts to improve things, whether the agency be the World Trade Organisation or the European Union. This is the ground where the Daily Mail meets Globalise Resistance, where Sir Bob meets Freddie Forsyth.

This may not be so surprising. Change, as Leadbeater says, threatens and removes the boundaries and borders which many of us find comforting. We find foreigners living next door, speaking strange languages, our currency disappears, our boring lifelong careers may become more exciting, more precarious portfolios. We will often attach a notion of deep history to a situation that was in fact quite temporary. Leadbeater's example is the insulated, protective nuclear family, as fetishised by writers like Melanie Phillips, which – in its most conservative form – is a very recent invention.

Militant pessimism seeks to withdraw. It attempts to create fortresses, whether they be fortress sterling, or an asylum-seeker-free Fortress Europe. It seeks to leave Kosovo and Bosnia alone because our interference will always make things worse. It pulls the covers over its head and hopes that its nightmares will go away.

I am, of course, an occasional pessimist. I don't live my life in a state of Fotherington-Thomas ecstasy, blowing kisses to the sky and trees. I couldn't be a columnist if I did. I can see where a certain kind of facile optimism, such as that which fuelled the dot.com bubble, can lead us. But I am excited by change, by biomedicine, by how the communications revolution has given power to the citizen and not the government, and by the fact that the world has put Milosevic on trial. I see the need now, to turn all this outwards, towards the world.

So I feel assaulted by this great, crushing, black wave of pessimism, administered to me in the twin daily doses of the tabloids and the Today programme. The forces that will be strengthened, emboldened, given new life by a No vote will be precisely those that want most to put up the shutters. It's the forces of pessimism, Comrade Bob, that will kill any grand attempt to help Africa.

David.Aaronovitch@btinternet.com