I've watched both of ISIS' beheading videos, and ISIS' purpose is clear. American forces just need to leave. But of course, if you repeat this to the mainstream or the status quo, you're instantly labeled a "terrorist sympathizer" or something like that.
So just remember in this time, when you try to educate/persuade these people, remind them history didn't start on 9-11-01.
If I was President, I would gladly accept ISIS' request. I would pull all the troops from around the world. I would let ISIS "win". Who cares? Because terrorist threats on the U.S. would immediately decline as we no longer act as the World Police. The Middle East can deal with their own problems.