But they aren't.
If you look at the history of Islam, it began with blood and destruction. Muslims say "Peace Be Upon Him" when they mention the prophet Mohammed, but Peace is not what Mohammed brought to the seventh-century world in which he lived. He was a warrior who brought death and destruction. His message was "Kill them (unbelievers) wherever you find them," which is what Islamic State, in his name, are doing now - bringing death and destruction to their fellow Muslims as well as to the Yazidis and Christians in Iraq and Syria and soon Turkey. These horrible photos - I'm sorry if they disturb you - are proof that IS has returned Islam to its seventh-century roots.
Jesus Christ did not preach destruction; his message, not an easy one, was a message of peace: "love your enemies ... do good to those who hate you". But destruction and retribution have often been carried out in his name, acts which blaspheme the message he brought to the world.
Moderate Muslims - of whom there are millions - need to stand up and declare that the faith of these terrorists is not the faith they wish to belong to. They can find a few of the Prophet's gentler sayings (there aren't many) to shore up their belief.
More than a million people (I was one of them) marched in the streets of London in 2003 against the Bush/Blair invasion of Iraq. Tens of thousands of Kurds and their supporters have demonstrated around the world in the last few days to call for logistical support to defend the beleaguered Syrian town of Kobani against Islamic State. We need to hear them. IS threatens the world - East and West - far more than Al-Qaeda ever did. Their 'Caliphate', if we do not halt its expansion, will eventually turn its attention to Israel, the most hated enemy of jihadists, the enemy with the most nuclear weapons in the Middle East. The Kurds of Kobani will not be able to hold off IS on their own.
At the end of my 1999 'Arab Spring' novel Shaikh-Down I offered a vision of the world after Armageddon in the very near future. Damascus, Mecca, Jerusalem: all destroyed. Arabia - from the Gulf to the Mediterranean - turned into a vast radioactive desert. This is where Islamic State, in the name of Allah, are taking us. They must be stopped.