Dr. Rouhani , president of Iran, spoke at UN in Sep 2014. The full text is also available at his website, http://www.president.ir/en/81324.
Here is a piece of it which clearly states that what IS is doing is very wrong: [[of course most muslims do know this but how can the IS can find followers in Europe is just not clear to me]]
To fight the underlying causes of terrorism, one must know its roots and dry its source fountains. Terrorism germinates in poverty, unemployment, discrimination, humiliation and injustice. And it grows with the culture of violence. To uproot extremism, we must spread justice and development and disallow the distortion of divine teachings to justify brutality and cruelty. The pain is made greater when these terrorists spill blood in the name of religion and behead in the name of Islam. They seek to keep hidden this incontrovertible truth of history that on the basis of the teachings of all divine prophets, from Abraham and Moses and Jesus to Mohammed, taking the life of a single innocent life is akin to killing the whole humanity. I am astonished that these murderous groups call themselves an Islamic group.