I've resisted rushes to judgment regarding recent terrorism and related activity. My view is, suppose we (military powers) were decided and did clear out Syria and Iraq of the Islamic State, and set up areas where people could rebuild their lives (could be a good idea): what difference would it make to these ideologues operating out of European capitals and other cities?
As for them not being in any way representative of Islam... Well, the IRA used to compromise the Roman Catholic Church (among this Church's other morally dubious internal activities) but the IRA never fought in the name of Roman Catholicism. Islamic State does, and it is one of the children of the Wahabi type approaches to Islam exported from Saudi Arabia, essentially one of the products of Western Imperialism. The Qur'an contains some pretty nasty texts, as does the Bible and even the Bhagavad Gita set in a civil war scenario has Arjuna telling Krishna that it is his duty to fight. The 'religious classics' as David Tracy has them can motivate in multifarious ways. So it does matter that Muslims condemn Islamic State and why, just as Christians ought to condemn the Klu Klux Klan and any form of Christian based ethnic superiority (take the Yugoslav break up as a time when such did not happen). Islam - Salam - should be a religion of peace (with conditions regarding its freedom to operate) but it is, unfortunately, up to Muslims to proclaim this.
For too long, since the Renaissance, Islam has had a chip on its shoulder. The 'final revelation' (also it believes it was the first) was superseded culturally and intellectually by the West. Things really went wrong after the end of the Ottaman Empire and some pretty silly boundaries for Arab and other States post World War I that ended up being ruled by political thugs. The failure of the Arab Spring is a failure of those States as conceived - Egypt should have done better. The result is that Islam continues to dig itself in a hold. For too long it has clericalised and intellectual centres in the east have contracted and been suspicious of Western Islamic intellectuals. Reform is now more than necessary.
The danger is that Islam gets regarded today as Roman Catholicism was regarded at the time of Elizabeth I. This would be tragic and unnecessary. It is already going that way in France, with its secularism tradition - thus Islam becomes a threat, thus extremists target France in particular. Islam is in need of a Reformation, just as a corrupt Christianity had to reform. If it doesn't, it will end up being the loser, it will lose moral authority. The reform has to relativise Islam, see the Qur'an as historical and not perfect, actually teach its content more widely to believers rather than its repetition, and tackle the questions around absence of archaeology regarding the founding years of Islam around Makkah and Madina.
This terrorism will pass because it is a condition of the current condition of Islam and political forces. The lunatics running this particular asylum are young and will rotate through. But the damage done to Islam could be much the greater, unless its adherents address the need for liberating reform - to attempt to return to that intellectual and artistic culture of its heyday, when it could tell an intolerant Christianity a thing or two.