Anyone who ever defends the ISIS (Iraq Syria Islamic State) should open their eyes and hearts that this group is nothing but a gang of terrorists. They do not defend Islam, not fight to glorify Islam, but only to the greatness of their own group.
They kill the innocent people, women and children, and destroy prayer houses. In fact, Rasulullah Muhammad mandated his soldiers in wars to not destroy the prayer houses and kill women and children.
Most recently, they killed (beheaded) an American Muslim, Peter Kassig, who worked in Syria as a humanitarian worker. I do not know, whether the recording was true or not. The recording could be modified by Americans themselves to give the impression that the ISIS not only kill non-Muslims but also Muslims.
If it’s true then it’s the task of Muslims all over the world is to prove the truth. But if ISIS did killed him then it only proves their barbarism. How can a Muslim kill other Muslim who is not guilty? Didn’t the Prophet himself forbid his troops to kill unbelievers who said ‘La ilaha illallaah‘ (there’s no God but Allah) on the battlefield, even for whatever reason.