The cry of "You ain't no Muslim, bruv," most certainly summed up the anger of most Muslims throughout the world at the violence being committed by terrorists in the name of their religion. They were the right words for the moment. However, the Islamists who are responsible for the bloodshed are Muslim. Their understanding of Islam informs their actions and they could find as many quotes from the Q'ran endorsing violence against "the infidel" as peace-loving Muslims could find quotes condemning murder.
It is of the utmost importance that Muslims do not sweep the problem of Islamism under the (Persian) carpet by claiming that the terrorists have nothing to do with them. Instead, peaceful Muslims need to accept that there is a cancer spreading through their community of faith and do something about it. They need to accept that their scriptures contain texts of terror and they need to develop a hermeneutic that allows the condemnation of such texts. This has to be done universally and at the highest level of authority. My fear is that, as long as the Islamic world is predominantly ruled by dictators with the backing of their religion's leaders, who willingly employ state murder as a tool of control, it is extremely unlikely that this could ever happen. However, those Muslims who now enjoy the freedoms that come with residence in democratic countries, could start the ball rolling. In the UK they could stop importing conservative imams from Pakistan and employ, instead, English speaking progressive imams at their mosques. At the moment I fear that although most Western Muslims condemn the terrorists they still hold to the conservative Islam that so easily leads to extremism.
Of course, Islam is by no means the only religion with an extremist problem. Hinduism, Judaism, Christianity and even, of all things, Buddhism have their bad apples. For example, people from my own religion, Christianity are regularly responsible for the murder of their fellow human beings, either directly as in the case of the murder of family planning clinic staff or indirectly, as in the case of their homophobia giving bigots implicit permission to beat up and often kill gay and transgender people. I am often tempted to declare that these people are not really Christian and I could find plenty of texts in the Bible that would support such a condemnation. But as with the Islamists, fundamentalist Christians can also easily find many texts in the Bible that support their, what I think hateful, views. The killers within the Christian faith are fully paid up Christians and I would not be helping the situation if I was to claim otherwise. It is better for me, and other non-fundamentalist Christian commentators, to acknowledge the cancer that is within the body of the Christian faith and acknowledge that the causes of the tumours are the texts of terror of our scriptures.
It is now possible to be a Christian without taking literally every word of the Bible. It is not impossible for a reforming Islam to have a similar, enlightened relationship with the writings of its past. To be able to do this Muslims will have to accept that their scriptures contain ambiguity and, even, error. Pretending they do not will be, ultimately, as useful to the cause of peace as pretending that bad people cannot be Muslims.