THERE are few signs of life at the Stockwell Green mosque in south London at the moment. The gates are padlocked and the telephones have been disconnected. And some hope it will stay that way. For the mosque is at the centre of a dispute within Britain’s Muslim community over how it should respond to the murder of a Muslim shopkeeper in Glasgow on March 24th. The killing was particularly shocking because the victim, Asad Shah, was a member of the pacifist Ahmadiya sect, and his assailant was a Sunni Muslim from Bradford. The Ahmadiya have long been harassed and discriminated against by mainstream Muslims in Pakistan and Indonesia, and this has often turned to violence. But this was the first time it had happened in Britain.

The weeks since have led to some self-examination among Muslims. But to prevent another atrocity, outsiders say the bigotry that might have contributed to it now has to be tackled head-on, beginning with the Stockwell mosque.

The Ahmadi consider themselves Muslims, but differ from the Sunni and Shia because they believe Mirza Ghulam Ahmad, a 19th-century Indian who founded their tradition, was a latter-day prophet. In many Muslims’ eyes, this makes them blasphemers. Pakistan’s Ahmadis, of whom there may be 4m, were declared to be non-Muslims by the government in 1974; in effect, their faith has been criminalised. There are about 25,000 Ahmadis in Britain, which has become something of a refuge from the violence of Pakistan.

Yet it is now clear that the sectarianism of Pakistan has pursued them to Britain, particularly in the form of the Khatme Nubuwwat movement, with which the Stockwell Green mosque is associated. The purpose of the movement (meaning “finality of the Prophethood”), which one official says started in Britain in 1983, is to refute the claims of the Ahmadiya, and to inform all Muslims that they are in fact “traitors to Islam”, as the Khatme Nubuwwat Academy’s website reminds everyone. The same website helpfully lists all the fatwas against the Ahmadi in Urdu, English and Arabic. Readers learn that the “dangerous” Ahmadiya (called by a derogatory term) are a “destructive” sect with a “filthy agenda” that helps Zionism. Muslims are urged not to have anything to do with them.

One imam at the academy, a modest place in east London, argues that all this is merely “academic”, a learned refutation of Ahmadiya doctrine. However, after the death of Mr Shah the Ahmadi are asking whether this sort of propaganda is brainwashing young Muslims and inciting them to violence. The Muslim Council of Britain (MCB) has been criticised in the past for not acting to counter it. This is partly because it does not recognise the Ahmadis as Muslims either; but it has condemned Mr Shah’s murder, and insists that the Ahmadis can be argued against “without vilifying or demonising them”. To this end, it has suspended the Stockwell Green mosque’s membership of the MCB and has set up a panel to investigate whether it was inciting hatred. Leaflets calling for the killing of Ahmadis if they did not convert to mainstream Islam were found in the mosque after the murder of Mr Shah.

This response is too lame for some, however. One activist, Sadaf Ahmed, has launched a petition for the government to conduct an official investigation into the activities of Khatme Nubuwwat. She points out that the group’s speakers travel freely to Britain to vilify the Ahmadis. Qari Hanif Qureshi, a hate preacher who called for the death of Salmaan Taseer, an ex-governor of Punjab who challenged Pakistan’s blasphemy laws and was murdered for it in 2011, spoke on May 4th at Luton mosque. Ms Ahmed argues that “If we replace the word Ahmadi in any of the Khatme Nubuwwat’s speeches or literature with Jew or Muslim or Hindu, we’d be disgusted at their hateful rhetoric.”

Many Ahmadis are concerned that too much casual denigration—posters in shops urging Muslims to “beware” of them, for instance—goes unpunished in the name of free speech. They fear that if the authorities, both Muslim and secular, don’t crack down now, then tolerance of such intolerance will simply lead to more murders.