SINCE there seems to be a smartphone app for just about everything, Buycott shouldn't surprise me.

The technology is American, the name is awful, and the possibilities endless. In a world that confuses a casual touch on a glowing screen with activism, the thing is almost perfect.

With Buycott, the concerned consumer can get serious. Join a campaign on buycott.com, scan the barcodes of products that trouble you, and the app will confirm or refute your suspicions. Then, with your conscience clear, you can reject or accept the goods on offer. We've come a long way from searching out those Produce Of South Africa labels.

Two campaigns are trending, as they say, on Buycott at the moment. In terms of app-wielding members, Long Live Palestine Boycott Israel and Avoid Israeli Settlement Products easily outstrip the likes of Boycott Coca-Cola and Boycott Nestle. At the time of writing, the first anti-Israel effort had 229,558 members, the second 121,641. That's a lot of smartphone users.

You could mock them, of course. Scanning barcodes among the fruit and veg doesn't sound like the way to stop an Israeli tank. Benjamin Netanyahu's government probably does not have self-righteous consumers on its list of worries. Besides, as Israel's friends will surely mention, any economic damage you inflict will fall on the many Palestinians who have no choice but to work for Israeli firms.

These are not new arguments. Margaret Thatcher used to squeeze out a realistic-looking tear when sanctions against apartheid South Africa came up. Those measures, along with boycotts in sport, culture, groceries, banking - you name it - would only hurt poor black people, she'd say. As critics of this week's raising of the Palestinian flag above Glasgow City Chambers have also insisted, these were gestures. They did no real good and might well do harm.

As it turned out, racist South Africa didn't like being isolated. It suffered economically, but the psychological effects were almost as profound. The dominant caste of the apartheid state were left under no illusions about the contempt in which they were held. It rankled; it undermined their self-belief. In the end, even the racists saw reason.

Something else was brought home to them. Amid the boycotts, all manner of connections stood revealed. The nonsense of setting "politics" to one side while the cricket or the Sun City cabaret went on became untenable. Everything counted. It was one thing to be crippled economically, but a pariah state was left without the consolations of culture, sport, or anything else. It was no longer allowed to pretend that it was a normal society.

There are plenty of arguments, good and bad, making the distinction between the old South Africa and Israel. The latter has democracy and, in law, equal rights. It has the debris of thousands of Hamas rockets on its territory. In that organisation Israel faces an enemy whose taste for Holocaust denial is as racist as anything ever conjured by the apartheid regime. And Israel, say its friends, is above all the victim of outrageous double standards.

None of that has halted demands for action. The Boycott, Divestment and Sanctions movement has called for the shunning of Israel in culture, commerce and academia. On the one hand stand intellectual and artistic liberties, the freedoms that must at all costs be preserved, so it is said, not least in times of bitter conflict. On the other side of the gulf there is ruined Gaza, the collective punishment of a people, and 1800 dead, 408 of them children.

Last week, a tiny grant - reportedly of around £1400 - given by the Israeli embassy to the UK Jewish Film Festival caused a huge row on the London arts scene. Claims of censorship and anti-Semitism flew after the Tricycle Theatre decided it could not show the festival's movies, as it has done for eight years, unless the money was returned. The festival refused.

Jonathan Levy, chairman of Tricycle, said that, because of the Gaza carnage, the theatre "cannot be associated with any activity directly funded or supported by any party to the conflict … The Tricycle will be pleased to host the UKJFF provided that it occurs without the support or other endorsement from the Israeli government".

In a press release, the festival responded by pointing out that it is "apolitical" and has long been "showcasing perspectives from both sides of the conflict". The statement added, however, that the film event "has received support from the Israeli embassy for the last 17 years, portraying the unmistakable cultural connection between Jewish people and the State of Israel".

The first question is the biggest: should cultural work ever be boycotted? Should the connections forged by free and creative minds, human being to human being, ever be severed? The same question applies to exchanges between academics. What is gained - and what is lost - by curtailing the flow of knowledge?

Such inquiries are supposed to lead to noble conclusions. Who dares gag poets? Who suppresses the philosophers or film-makers? And where do arts bureaucrats get off telling a movie festival how it must arrange its affairs?

Those questions get us nowhere. If accepted, they mean that sanctioned representatives of any regime are granted an open invitation in all circumstances. So let the totalitarian dictator send his ballet troupe. Forget what he's done to his people; listen to the melodies his favourite composer has devised. And grant the dictator the pretence of respectability.

Boycotts are satisfying, but not subtle. Why just Israel? That state's supporters are quick to identify anti-Semitism and too often they are right. Where's the boycott of the military junta in Egypt that tortures its opponents and hands out death sentences to hundreds? What remains of Western angst over the thuggish Chinese regime? Israel's deeds do not constitute the only vile acts in the Middle East, far less the world.

As The Observer's Nick Cohen remarked in The Spectator last week, Tricycle takes hundreds of thousands of pounds in funding from the British state. That same state engaged in the illegal war - one that Cohen supported - in Iraq. So why is the theatre's board also accepting state money?

Once begun, boycotts never end. Tit for tat comes easily to lousy regimes keen to remind us that no government is without sin. What entitles the West to its hypocrisy? Irrespective of the source, that's a fair challenge, but one with dismal consequences. It means we shut up, say nothing, allow everything, and become complicit.

There are double standards: true enough. Anti-Semitism is abroad again in Europe: also true. But despite every effort of Israel's government to pretend otherwise, Jewish people and the State of Israel are not one and the same. Arguments over the fact have been going on in the country since the Palestinians were first dispossessed. Boycotts hold the state, in all its guises, sponsor of culture and war machine alike, to account.

There are 1800 dead in Gaza because flattening that enclave has become Israel's habit, and because Israel has no intention of allowing a Palestinian state. A movie festival is not worth the life of a child. Culture that is quarantined from reality serves no one.