Remove their religion and there is little reason to lop someone's head off screaming "Allah!" ISIS, while extreme, is not doing something entirely unique when it comes to harsh treatment of anyone they deem a problem. The entire idea of branding "religious extremism" is not new either. While I completely agree that Islam is furthest behind the evolutionary curve when it comes to growing up we have plenty of historical examples of just about all religions killing many while claiming "God's will." Fact is ISIS is not the first group to behead whomever they capture, nor are they the first group to take advantage of weakened leaders of these nations.
Remove all of our interference in the region headed back a very long time and odds are the landscape of the region would be very different. What is so inconvenient here for everyone is Obama is now the 4th president in a row to engage in military action somewhere in Iraq for some reason. You do not get to ignore all that history just because ole (D) and (R) is getting picked on politically. Like it or not, we have been playing over there for a very long time trying to instill our brand of western ideologies in a region made up with people with no aptitude for the said ideologies we are selling.
Another inconvenient truth is those that make up ISIS have been there a very long time and are now taking advantage of a long term civil war in Syria that we are not so responsible for, and a weak government and military in Iraq that we are entirely responsible for. Again, we do not get to re-write things today just because we are starting to realize what we have done (rather not done.) Our confusing and hypocritical foreign policy (under several Presidents now) has come back to bite us in the ass. Again.
Fact is the Iraq government we left behind is both incompetent and weak, and in that region of the world means all those ideological differences among the splinters of their faith are showing up. Look at those that make up ISIS today and you will find plenty of ties to the region depending on leader you want to discuss. Look all over the region as a whole and you will see a group of people splintered from various faiths that cannot and usually do not get along unless they are forced to living under someone strong enough by both military and religious means. You may not like all of this but an objective review of Middle East history (both long term and recent) confirms it all.
Case in point for it all, more people being beheaded.