Are we heading for a new barbarism? Is this the return of the 18th-century mob? Here are more questions than answers. I ask because when all the fuss about Emily Thornberry and her photo tweet from Rochester has died down, we shall be left with something more disturbing than whatever sin she may or may not have committed. We’ve just seen demonstrated the speed, the destructiveness, the sheer violence of the modern tempest that information technology can create. In the world of opinion, climate change has arrived already.

As a workaday columnist, I reflect that I could equally easily write a spirited defence of Ms Thornberry; or a spirited attack; or I could attack Ed Miliband for publicly laying into her; or for privately agreeing with her.

In the Telegraph Boris Johnson achieved all four within the compass of a single column. He argued that Thornberry was unlucky; that it served her jolly well right; that Ed Miliband shouldn’t have attacked her; and that he must secretly agree with her.

Well, it would be fun to tease Boris for running so nimbly with the hare and hunting so stylishly with the hounds. We may wipe a tear from the eye after reading his touching tribute to White Van Man (barely — but just — avoiding the phrase ‘salt of the earth’) while remaining doubtful whether, if a Johnson daughter declared her intention to shack up with a van man in Rochester who decorated his house with English flags, he would greet the affair with rapture. But we should not single Boris out. Horror at the match would be shared by the entire cabinet, the shadow cabinet, the editors of any of our newspapers, most Spectator readers and doubtless Nigel Farage too. Truly we are a nation of hypocrites.

But that’s not new. What’s new is the way IT can now turbo-charge national hypocrisy, turning it into a ferocious force within the space of a couple of hours.

Here’s a warning: a warning equally to those inclined to praise Emily Thornberry and those inclined to blame her; to those inclined to admire Mr Miliband’s prompt command and those inclined to mock it. It’s a warning to the likes of myself; and Boris, too, who will remember his run-in with Liverpool over Hillsborough and the late Ken Bigley a decade ago, and will ask himself whether in an age of Twitter he would even have survived. It’s a warning to left and right, to liberals and conservatives, to black and white, feminists and sexists, racists and multiculturalists alike.

All should quail. For the mob is fickle and knows no single creed. It has no favourites — or rather its favourites may switch in the blinking of an eye. Its prey may rise from nowhere into sudden public contempt, and be forgiven as fast. One day the mob is with the fox, the next with the hounds. All you can be sure of is that if you attract the mob’s attention in the morning, by sundown you may have been smothered with kisses or beaten to a pulp.

And as 18th-century grandees may have peered nervously down from the windows of their dining rooms, always in fear of the gathering of the mob in the street, so in the internet age those who may be in (or have the misfortune to catch) the public eye can never be sure whence the next virtual mob may gather and strike. Those who call themselves reputation managers may become the new bodyguards against the footpads prowling the Twittersphere.

There are two keys to this dawning dynamic: speed and volume.

Until a few years ago, and for the whole of human history before that, inbuilt blocks, inefficiencies and delays acted to retard the spreading of — and reaction to — information. Word of mouth was very slow; manuscript was intrinsically slow; the printing press did accelerate the dissemination of news but there remained brakes to its speed, and very severe breaks to the spreading of public reaction to news. Letters to the editor were the closest we got to an internet flash mob.

Sound amplification, then broadcasting and the telephone, gave new wings to the spreading of report, but again there were limitations to speed and volume of response. We might know almost instantaneously that a murderer had been caught or a politician indicted; and know pretty fast what we thought about that. But it took much longer to know what everyone else thought. Opinion may echo and amplify with the knowledge of others’ opinion; waves of public indignation were hard to gather on the instant.

Street mobs in an earlier age, and radio phone-ins and pollsters’ reports in our own, have been the closest we got to that. There were inbuilt restraints to rapid report and reaction. Almost overnight, those restraints have gone. All at once I can know immediately what has happened, can know that everyone else knows too; can know their reaction; and know that they know mine. Tremendous self-reinforcing surges of anger, outrage — and indeed distress, admiration or generosity — can be the near-instantaneous result. We have no time to sleep on it and see whether we still feel the same in the morning: the wave is already breaking.

In this case it broke over Emily Thornberry’s head. Recently it broke, too, over the heads of the ‘pick-up artist’ Julien Blanc and the comedian Dapper Laughs. I regard both these characters as pond life, but there must be fairer ways of deciding whether to withdraw Blanc’s visa or cancel Laughs’s ITV show. It was crude volume that swung these decisions, with little thought as to how easy it might be to assemble the 150,000 signatures that did for Blanc, or the 60,000 signatures that finished Laughs.

And there but for the grace of God go I — and quite possibly you, reader — and certainly Boris. Will mankind learn to start ignoring these storms? Or will people start going down like ninepins? Or will everybody become horribly circumspect, like Winston Smith in Nineteen Eighty-Four confiding only in old friends in safe houses? Who knows? I end, as I began, with questions.