Matthew Norman: It's Tom Daley's Twitter tormentor who needs the law's protection

We had Danny Boyle's version of what it means to be a young Brit in the age of instant communication the other night, with that thrilling song and dance text messaging sequence. Today, as if some malevolent cosmic law dictates that inspiring idealism be balanced by brutal realism, we gaze upon the Frankie Boyle tweeting troll version of the same.

Curiously, it isn't the Glaswegian comic who has been arrested under the supposedly benevolent earthly law that apparently elevates casual cruelty on Twitter to a criminal offence. Why he remains at liberty after renewing his typically fearless campaign to distress the adorable Rebecca Adlington about her looks, with a tweet likening her features to those of a dolphin, is anyone's guess.

Perhaps this oversight will soon be corrected. Being "offensive" is enough to get one nicked under the relevant Act, and the swimmer makes no secret of how hurtful she finds these Wildean thrusts. For now, the honour of being the only person nicked for Olympian idiocy of this kind rests with the boy arrested in Weymouth yesterday for upsetting Tom Daley.

The unnamed 17-year-old "man", as police statements drolly like to describe the teenage male, tweeted Daley, as you know, to rebuke him for "letting down" the father who died last year by failing narrowly to win a medal in the synchronised diving. In a later tweet he wrote: "I'm going to find you and I'm going to drown you in the pool...". Little space need be wasted on acknowledging that this melded the cretinous with the vicious.

Less crushingly obvious, though not much, is the role of the law in such a case. The question here is a variant of the middle-aged columnist's ancient fall-back rhetorical question about the increasingly youthful appearance of officers: is it just me, or are policemen getting stupider?

In the Dorset town hosting the regatta, the constabulary sailed boldly back into the same sea lane of deranged overreaction they explored recently by shutting a motorway, and detaining coach passengers for hours, because someone's electronic cigarette emitted a wisp of atomised water resembling smoke.

There are more intelligent creatures crawling about under paving stones, to misquote Sybil Fawlty's analysis of an errant builder, than whoever dispatched officers to a Weymouth B&B to question this boy on suspicion of "malicious communications". Forgive the rancorous tone, but I resent being reduced to sub-Littlejohnian ranting by events of such auto-satirical absurdity that, while you certainly could make them up, you wouldn't bother on the grounds that they are too crude to warrant the effort.

Less tranquillisingly dull than the police's inability to distinguish infantile nastiness from what could be construed as any of their beeswax is the vexing question of where freedom of expression ends on social networks. In the wondrous isle of D Boyle's creation, every one of us has the innate grasp for irony to tell apart a frustrated passenger's jokey promise to blow up an airport from a genuine security threat. In the septic isle personified by Mr F Boyle, taking pleasure from bullying people about their looks and parental bereavements and taunting children for being born with grave physical disabilities is one national sport at which we are seldom off the podium.

Which interpretation comes closer to the truth is impossible to know, though I suppose, in the Olympic spirit, we must try to be optimists. But to realists who appreciate that the two will always co-exist, it seems entirely in keeping with Danny's Utopian vision of mature, modern Britishness that sledgehammers are never taken to crack nuts even as rancid as Frankie; that the tolerance so stirringly celebrated on Friday night must extend even to those to whom one might privately fantasise about taking the business end of a baseball bat.

You cannot legislate the wickedness out of people. You possibly could legislate to make websites remove the cloak of anonymity (though considering how Twitter dobbed in our own Guy Adams to NBC, and presumably the Weymouth boy to the fuzz, they seem as happy to do it themselves as Google is to cooperate with the Chinese authorities). But this, in a small but significant way, would be an infringement of a civil liberty. Anonymity is a right, or should be, and the flip side of welcoming it as a force for great good in Tahrir Square and Tehran is accepting that it will be hatefully abused elsewhere.

Where legislation may be required, in the absence of a police force, DPP and even judges with a shred of common sense, is to protect not the victims but their tormentors. The freedom to cause offence is not one in defence of which many would march on Parliament, but it is a human right all the same. It is not, of course, indivisible. When racially aggravated, as with the imprisonment of the man who rejoiced in Fabrice Muamba's apparent death, it merits draconian treatment, just as it would had Liam Stacey been overheard screaming the words in the street rather than tweeting them. Whatever is already a crime, be it homophobic abuse, threats of violence (credible ones, that is, not facetious ones about airports or not wildly implausible ones to drown one of the world's best aquatic athletes) or defacing photographs of the deceased, is a crime regardless of the medium used to commit it. Telling Tom Daley that he let his late father down, however distasteful and unpleasant, is not a crime. The eighth-witted child's punishment if and when his identity leaks out will be worse than a few weeks in jug. Those who wish to live by digital mob rule may metaphorically die by it.

Albeit, please God, that we are more discerning in our targets and restrained in our language, columnists like myself cause offence almost as a matter of honour, so perhaps this argument comes lightly dusted with self-interest. On the message boards beneath the articles, meanwhile, even the sweeter among us are often slaughtered in the most personal terms. No one relishes the process, or fails to be depressed by the incoherent rage and scattergun spite with which a small but tireless regiment of inadequates cock their legs over one forum after the next, and mark them with their scent.

It is the way of the world that some people are poisonous, as it has always been, and Twitter is merely the most effective conduit for human venom yet invented. This is something with which this green and pleasant land must learn to live. If the price of one Danny Boyle is 100,000 Frankies, we'll just have to pay up.