I see you've returned after a long absence...
Islam by its nature is actually not violent, and neither are the majority of the people who call it their religion. But as with nearly all religions, there are factions that are more extreme and more radical in their interpretations of their religion and what it stands for. It wouldn't take a lot of effort to find similarly radicalized elements within Christianity, Catholicism, Judaism, etc. The major difference is that this faction is running around publicly killing people in a country that was apparently though to be reasonably "pacified" until now.
In simple terms, don't throw out the baby with the bathwater.
As I've been led to understand it by domestic media, ISIS is the Islamic State of Iraq and Syria - the group is seeking to create said state and to run it under a strict version of sharia law. It's actually people from outside of Iraq that are inciting a lot of what's been taking place, using disaffected Iraqis in much the same way that Hitler used the people under his rule to seek to create his vision of an empire, and throughout history I'm certain there are many other attempted and succeeded dictatorships, juntas, etc. that have done the same.
One should never judge a religion followed by millions of people by the acts of a few thousand people being led by zealots and madmen. In fact, who really has the moral high ground by which to judge any religion? You can determine whether it's a religion that's in line with your beliefs, you can decide whether to raise your children in that religion, but anything beyond that and you're seriously reaching. It's the judging of religions that creates these situations in the first place.