I'll go you one better: It was carried out by Muslim extremists but it was financed, encouraged, excused, and approved by Muslims all over the world. Not extremist Muslims. Muslims.
If Islamic leaders do not agree with these lunatics then they should be leading the charge to rid this world of these extremist who have commandeer their faith and are turning it to evil acts in the name of the Almighty. They must join us in this fight; they must lead it in their countries.
If they refuse to actively participate in the eradication of the combatants, then they are supporting them and they too should be considered the enemy an eliminated.