Let's begin with 1989: a year currently being celebrated for the fall of Eastern European Communism, but on the home front, remarkable for slightly less respectable reasons. It was that year, after all, that saw the peak of the great youthquake known as acid house, and a recreational drug culture that had begun as the preserve of a few thousand metropolitan libertines decisively soak into the mainstream. Not that things were quite this simple, but it isn't a bad theory: if you want to understand the modern ubiquity not just of ecstasy, but cocaine, cannabis and LSD, think back to the teeming crowds that would gather for illicit raves, a milieu that came to all but define the UK's cultural cutting-edge, and a political and media class that was quickly scared out of its wits.

Inevitably, a culture that was held up as being utopian soon turned cheap and nasty, but its legacy was unstoppable. At the last count, surveys suggested that 2.39 million Britons have tried ecstasy, and 470,000 of us have used it in the last year. It's been a long time since I had any, but I would imagine that, with the exception of either the reckless or unlucky, what most of those people experienced was entirely benign: the usual hours split between a euphoric rush, a pleasantly soft landing, and much less of a hangover than one would get after a night's hard drinking. What they took did not lead them into life-threatening addiction, or get in the way of family or work. Moreover, most will pass through their E phase, and then quietly calm down.

The same applies to the vast majority of the 3 million people who have smoked cannabis in the last 12 months, or – dare I say it – most of the 7% of 16-24 year-olds who have recent experience of cocaine, and may have found that it turns them into a crashing bore, but have become neither addicts nor vagrants. So here's the question: why do people in power persist in painting those Hogarthian pictures of one small taste of this or that leading inexorably to the gutter, and worse?

Such is one of the most depressing aspects of the David Nutt affair – symbolised by both Gordon Brown's now-infamous claim that cannabis could be "lethal", and Alan Johnson's Guardian letter linking Nutt's views on the relative dangers of ecstasy and horse riding with "thousands at risk of being sucked into a world of hopeless despair through drug addiction". This is bilge, and if the home secretary is as savvy as some of his fans suggest, he must know it.

Obviously, a whole demonology underlies this mess. With all the hysteria that a life spent in thrall to a handful of newspapers demands, our politicians still sweep up the recreational pharmacopeia into the same political receptacle as much more harmful substances, and thereby hope to keep the right kind of voter on-side. Woe betide the MP who attempts anything more sophisticated – as evidenced by innumerable Labour election campaigns that target opponents for being "soft on drugs".

If you want a particularly depressing illustration of why the pursuit of power entails truly moronic manoeuvering, consider our likely next prime minister: as a backbencher, David Cameron made reasonably enlightened noises about the broken-down state of drugs policy, whereas now, the party he leads endorses the government's treatment of Professor Nutt, and biliously promises the usual crackdowns.

Meanwhile, on the Today programme, Nick Robinson voices the default position of politicians by claiming that drugs policy is something about which the public "cares passionately". Really?

It might sound like so much stupid optimism, but just as happened with suicide, divorce, abortion, gay rights and every other liberal bugbear of the last half-century or so, as the generational clock ticks on, this disconnect between public sentiment and the opinions of a terrified Westminster elite surely won't last. Keeping the debate within parameters defined by Richard Littlejohn, Paul Dacre and a few rent-a-quote MPs cannot work; the fact that their stance both demonises and criminalises millions of sons, daughters, fathers and mothers will eventually push it to the margins. And unexpected aspects of the debate may yet turn critical; like, say, the fact that while boozed-up multitudes still fill up with discount alcohol every weekend, the voices – like Professor Nutt's – that suggest this is a bigger problem than most recreational drug-taking are made out to be heretics (incidentally, consider that great puritan Brown's record on the alcohol trade: during his time at the Treasury, duty on beer was increased only in line with inflation, moves on wine were hardly punitive, and from 1998, the duty on spirits was frozen).

Of course, that isn't to suggest that any honest and reasonable conversation about all this will be easy. Between the crackdown merchants and those swashbuckling libertarians who shout "legalise the lot" (how, you can only wonder, would that work with crack?) there is political terrain that hasn't even begun to be mapped out. Certainly, if this small island is to re-orientate its drug laws, it will presumably do so in the context of some terrifyingly difficult international re-alignment that will have to happen in Europe, and beyond – all the way, in fact, to those far-off fields where drug-crops are temporarily killed off, only for the trade to carry on as usual.

What matters for now, though, are the terms of the debate, and a stand-off between a country whose habits decisively changed two decades ago – and politicians who apparently think the public is stuck not in 1989, but somewhere around 1954.