These people are freaking nuts! How can they realistically say these is in the name of Islam? These people are not normal, what is frightening is that the only thing that will appease them is if the kill the lot of us and then of course kill each other. I far as I can deduct, it is that we MUST kill all of them before they have a chance on any of us.
If only there were an easy, simple solution. Unfortunately, there is not. It is certainly necessary for SOMEONE to fight them on the battlefield to deny them the resources to continue expanding. However, unless and until they strike HERE, it is not our fight, simply one in which we hope one side wins. And if they DO strike here, our response should be to punish the ones who are responsible here, not to try taking over entire countries.
On the other hand, when we do kill any of their leaders, they recruit more members through their propaganda, painting us as the killers of innocent civilians in their countries.
Ultimately, the people who have been forced to live under them will have to put enough strain on their resources through resistance movements and non-cooperation, to cause their collapse. And this has already started to happen, although it will be a slow process, like the decline and fall of the Soviet Union was.