The Shahbag junction in Dhaka has become Bangladesh's Tahrir Square. Hundreds of thousands of young protesters are occupying it and raging against radical Islamists. Even sympathetic politicians cannot control the movement. The protesters damn them as appeasers, who have compromised with unconscionable men.

Theirs is a grassroots uprising for the most essential and neglected values of our age: secularism, the protection of minorities from persecution and the removal of theocratic thugs from the private lives and public arguments of 21st-century citizens

Naturally, the western media show little interest in covering the protest. The indifference is all the more telling because the Shahbag movement is a response to a crime westerners once deplored, but have almost forgotten.

The young in Dhaka have revolted over the war crimes trials of members of Jamaat-e-Islami. That useful leftwing term "clerical fascist" might have been invented to describe what they did. In 1971, the oppressed "eastern wing" of Pakistan rose against its masters to form Bangladesh. The Pakistani army responded with a campaign of mass murder and mass rape, which shocked a 20th century that thought it had seen it all. George Harrison and Ravi Shankar, the Bonos of their day, organised benefit concerts at Madison Square Garden. The murder of Hindus and Christians, the flight of refugees and the chance to weaken Pakistan pushed Indira Gandhi into one of the finest actions of her murky career. She sent the Indian army to liberate the tortured land.

The Pakistani occupiers were helped at every stage by Islamist activists. Jamaat took its inspiration from Abul Ala Maududi who has as good a claim as anyone to be the founder of political Islam. Maududi wanted a global war to establish a caliphate. The break-up of Muslim Pakistan impeded the prospect of a world revolution. To prevent this reverse, his followers formed death squads to slaughter the intellectuals, engineers, administrators and teachers who could make an independent Bangladesh work. The outcome of a belated trial of handful of Jamaat war criminals has set Bangladesh on fire.

As with popular revolts throughout history, Bangladeshi liberals are in two minds about the Shahbag demonstrations. On the one hand, they cannot fail to admire the determination of the young to state loudly and clearly that "religion-based politics had poisoned society", as Zafar Sobhan, editor of the Dhaka Tribune put it. On the other, the demonstrators are saying with equal force that they want the death penalty, that most anti-liberal of punishments, applied to the war criminals without mercy.

Do I hear you say that Bangladesh is far away and the genocide was long ago?

Not so far away. Not so long ago. And the agonies of Bangladeshi liberals are nothing in comparison to the contradictions of their British counterparts.

The conflict between the Shahbag and Jamaat has already reached London. On 9 February, local supporters of the uprising demonstrated in Altab Ali Park, a rare patch of green space off the Whitechapel Road in London's East End. They were met by Jamaatis. "They attacked our men with stones," one of the protest's organisers told me. "There were old people and women and children there, but they still attacked us."

The redoubtable organiser is undeterred. She and her fellow activists are going back to the park tomorrow for another demonstration. Her friends are worried, however. They asked me not to name her after unknown assailants murdered Ahmed Rajib Haider Shuvo, one of the leaders of the Dhaka rallies, on Friday.

Whitechapel was where socialists and Jews confronted the British Union of Fascists in clashes that leftists mythologise as a grand moment of anti-Nazi solidarity. While they still talk about the Battle of Cable Street and remember 1936, it is far from clear to me where today's British left stands in relation to modern struggles against ultra-reactionaries.

Liberal muliticulturalism contains the seeds of its own negation. It can either be liberal or multicultural but it can't be both. Multiculturalism has not meant a defence of all people's rights to practise their religions and speak their minds without suffering racial or sectarian hatred. As events have turned out, it has led to official society picking the pushiest group of "community leaders" and honouring them.

In the case of British Islam, the anointed group was Jamaat-e-Islami, even though its British members included men accused of war crimes in Bangladesh. It was as if the establishment had decided that Opus Dei represented British Catholicism or Shiv Sena represented British Hinduism or the most bigoted form of orthodoxy represented British Judaism. The scoundrel left led the way down this murky alley, as it leads the way into so many dark places. Ken Livingstone and George Galloway have backed the Jamaat-dominated East London mosque, and Islamic Forum Europe, the Jamaat front organisation that now controls local politics in Tower Hamlets.

But to concentrate on the dregs of the Labour movement is to miss the point. Whitehall has been as keen on dealing with the allies of war criminals. Many East Enders have noticed that the Metropolitan Police seems less than anxious to follow up reports of menacing "Muslim patrols" or threats to drinkers at gay bars.

The moderate Muslims at the Quilliam Foundation told me that the status Britain had given to Jamaat helped push British Bangladeshis away from social democratic politics and towards radical Islam.

The British-Asian feminist Gita Sahgal launched the Centre for Secular Space last week to combat such indulgence of theocratic obscurantism. She told me that Jamaat perverts traditional faith and she should know. Not only did she name alleged Jamaat war criminals living in Britain for Channel 4 in the 1990s, she is also Jawaharlal Nehru's great niece and a distant relative of the Indira Gandhi who sent the army into Bangladesh. I admire Sahgal and Quilliam hugely, but they are mistrusted, even hated by orthodox leftwingers. The feeling is reciprocated in spades and perhaps you can see why.

Many do not want to talk about Bangladesh massacres that moved liberal opinion to outrage in the 1970s, just as many did not want to talk about Saddam Hussein's gassing of the Kurds in the run-up to the second Iraq war. These are politically inconvenient genocides they would rather forget.

The most bracing effect of the demonstrations in Dhaka and London is that the terror is not being forgotten and liberals are being forced to pick sides. Let us hope that they stop picking the wrong one.

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