ISIS is a terrorist organization for sure  I respect this man for his bravery and this would be a lesson for those brain less people who join ISIS without knowing what Islam says about violence Quran says  Killing one Innocent is as though as you killed the whole humanity and ISIS kill number of innocent people everyday and this proves they are not real Muslims 
Second  I have heard from many non muslims saying Muslims are supposed to kill Non muslims where ever they find them though this is a mis understanding which I want to clear here A verse in Quran was revealed during a war at the time of Prophet Mohammad in which the Muslims were ordered to kill the enemies but do not make any harm to childrens and women who could possibly be there for some reason  It is also mentioned at several places not to initiate a war before they start harming you Plus this verse was revealed only for that particular period of time  There is no verse in Quran which restricts a Muslim to be friend of non muslims or kill any person who is not a muslim These are all rumors and mis understanding which makes some people sick and they start playing hatred games 
Someone has rightly said Little knowledge of science makes you an atheist and indepth knowledge of science makes you a believer   
Respect each others religion and spread love