We have nothing to fear from examining the issue but the onus should be on those advocating reform to justify their case

We all face a difficult choice this morning. On the smouldering issue of drug legalisation, do we back the permissive instincts of Russell Brand and Michael Fabricant, the Tory MP with the unnatural blond hairdo? Or do we join the Daily Mail columnist and mental health campaigner, the level-headed Marjorie Wallace, in rejecting any move towards decriminalisation?

It's a tough one, a modern dilemma – which is why we call them dilemmas. There is a case for both arguments and powerful reasons militating against them too. That may be why, as Alan Travis reports, the Commons home affairs select committee, chaired by the irrepressible Keith Vaz, has merely urged a royal commission to consider the options.

In her Mail column, my old Guardian colleague Mel P has no doubt (she doesn't do doubt; I wish she would sometimes) that Vaz's committee is "pretending to be moderate and responsible in order not to frighten the horses" while covertly manoeuvring society into a position where it will accept the findings of a quickie (report by 2015) royal commission of the great and good.

That seems less than wholly likely in so far as the Mail itself reports that three of the committee's five Tory members opposed the commission proposal and will doubtless say if they sense a plot, not a bien pensant gesture. Restoration of class C status for cannabis – downgraded from class B to C and then back again in 2009 under wobbly New Labour – was recommended only on Vaz's casting vote. It sounds like the usual wholesome shambles.

The pro-reform lobby quotes cigar-addicted Ken Clarke's assertion that "the war on drugs" has been lost (it was never waged, replies Mel P) and is costing vast sums of money, endless misery and ill-health, loss of liberty and life. In Mexico alone an estimated 60,000 people have died in the latest cycle; Colombia and Afghanistan have been all but wrecked by the narco-trade.

Nearer to home young people get criminal records for smoking hash for recreational purposes, criminals are introduced to hard drugs – is cannabis a gateway drug? – in prison of all places. The quest for drug money drives vast amounts of petty theft and not-so-petty kinds. Crime gangs and global syndicates build vast, state-threatening fortunes on its back, its big fish rarely brought to court along with the mules and the petty dealers.

On some estimates there is $400bn-worth of laundered drug money in our not-so-respectable banking system. Via that route the drug lords threaten us all, users or not. Hyperbole? Not in a week when Silvio Berlusconi is threatening to resume polluting the political system of the eurozone countries. Is he a drug lord? No, but I am sure you get my drift.

Dreadful, dreadful. History constantly reminds us what a legislative disaster was the US experiment with the prohibition of alcohol sales between 1919 and repeal in 1933. It gave the Italian mafia and other bootleggers a foothold and a lucrative network they have never lost. Think of the bogus moral dilemma the mafia families debated when deciding whether to expand from prostitution, gambling, protection (etc) into drugs in The Godfather series.

So decriminalise – or even legalise – weed for personal use and focus on the real bad boys, crack cocaine and heroin, and the professionals, say reformers. Tax it and regulate it. Seems reasonable, even if one of its advocates is self-styled comic Russell Brand, who turned up to give evidence to Vaz's committee dressed like a drug dealer on vacation and called the MPs "mate".

It was, of course, Brand and Jonathan Ross who made the "prank call" to actor Andrew Sachs that prefigured last week's "prank call" from Australia to the late Jacintha Saldanha at Katie Cambridge's London hospital. Gratuitous cruelty, as we can now see, but anyone who thought it funny last week – or thought Brand's prank amusing – can't throw stones at the weeping ("we meant no harm") Sydney DJs this week.

Why is this relevant to the drugs debate? Because it serves to remind us all that we have widely differing levels of tolerance and resilience. On Twitter one lout assured me this weekend that nurse Saldanha should have "enjoyed the joke. Her reaction was completely OTT." Thanks for that, but Saldanha is no longer here to benefit from your manly ("pull yourself together, woman") advice.

The case against changing the law hinges in no small measure on that calculation. Many young people nowadays – here are the Home Office's latest stats – experiment with cannabis, most drop the habit, relatively few get seriously stuck into the hard stuff, though cannabis too is much stronger than it was.

There are also "legal highs" for clubbing to complicate the picture. Most kids seem to handle that junk well enough too, but there is a small trickle of Saturday night teen fatalities. Awful. Not as many as caused by excessive misuse of drink (or even tobacco), I hear you cry. Well, no. Fights, car crashes, liver disease, cancer, sterility, STDs … there's a lot that can be laid at the door of legal highs.

So society seems agreed that we should raise the price of drink (the coalition is consulting on 45p a unit, Scotland has pitched for 50p) and tobacco (relentlessly rising) and to signify social disapproval of excess – though Britain seems to tolerate public drunkenness and related disorder more than most comparable countries do. It costs the hard-pressed NHS billions.

When we're grappling with excess caused by legalised drugs – not to mention smuggling of legal-but-taxed tobacco and booze on an industrial scale – it is surely perversely optimistic to legalise/decriminalise another category. Our chief economic competitors, the Chinese, upon whom we imposed the opium trade 150 years ago to square our trade imbalances, must be rocking with gentle, ironical laughter.

And yet, I fail to see the danger in a royal commission to examine the evidence, as long as its members are substantial and expert people across a range of disciplines, the kind who are not bullied by governments or the Daily Mail, nor swayed by what fashionable opinion says in Hampstead or Hackney.

If nothing else, we might learn better how to promote more effective drug education and rehabilitation; might learn how to handle the link between drugs, crime and prison more intelligently. No one who caught Hardeep's Sunday Lunch programme on Radio 4 on Sunday (I was sorting out my tax at the time) could fail to be moved by the story of Pete and Will, the druggie burglar and his victim. We have nothing to fear from knowledge.

Why do it all again when so many commissions and reports have urged a more sophisticated approach only to see politicians panic or retreat under pressure from Fleet Street, a neighbourhood where substance abuse can still be pretty impressive, though far less than it was years ago? As with drugs – where ministers are claiming success after a sharp drop in usage – progress is being claimed even on consumption of booze.

Because attitudes change and circumstances change. Also because it is striking listening to the usual parade of experts to note that the mere mention of the Dutch or Portuguese experience brings a flurry of contradictory assertions. On Radio 4's Today on Monday morning Prof Alex Stevens, an expert criminologist from the University of Kent, dismissed the Mel P arguments over Portugal (where possession of cannabis for personal use is now an administrative offence only) as "spurious evidence".

Yet I did not find his explanations for inconvenient trends in Portugal wholly persuasive, which is not surprising since the prof is a partisan, and the capacity of the human mind, even the expert mind (would you believe it!), to believe what it wants to believe is infinite. So let's have another crack at the evidence.

Myself, I think the onus is always on those advocating a serious reform to justify their case rather than to take a leap into the dark in the current "hey, let's give it a spin" fashion, especially on issues so culturally divisive.

From AV voting to the euro and back again via elected police commissioners (let us hope the gathering storm clouds over cronyism disappear) and Scottish independence, we sometimes have to be reminded that it is easier to demolish than to build.

And the old fuddyduddies who rail against social liberalism aren't always wrong. Hard though it is to recall now without a shudder, not so long ago people were allowed public space and some licence to argue that sex with children is just fine. Nothing dates as fast as the trendy. Watch out.