I don't agree, with respect to reaching the conclusion that because the vast majority of Muslims are peaceful, which is undoubtedly true, that what these minority of Muslims are doing is "not Islam". When it comes to what is and what isn't Islamic it's a grey area. The leader of IS has a doctorate in Islamic studies, who's to say what he and his followers are doing in the caliphate is not Islam? from my understanding, some of the awful things going on over in Irag & Syria are very Islamic. I wouldn't reach the conclusion that smoking isn't bad for you because the vast majority who participate don't die or have ill effects.
It isn't Islam. They are actively trying to get the world to turn against them and Islam in the hope that the world retaliates at large and wipes them out, because they believe this will initiate the end times "as prophecised".
They are literally trying to get themselves killed because they believe orchestrating the "end of the world".
The kicker here is that a large amount of what they get up to is in direct contravention of Islamic law. They way they've been treating people, killing them indiscriminately. Things such as burning people alive.
They are predominantly killing other Muslims for boo reason other than chaos.
The prophecy is that the Christians wage war with the Muslims. Even if we assume this prophecy to be true, they aren't the Muslims because of their acts, and the west aren't the Christians because the majority of countries in the west are highly secular and the population is culturally Christian in as far as a few misappropriated traditions that are tenuously tied to Jesus.
Those waging war against ISIS are not doing so in the name if Christianity, so as above even if we do assume the prophecy to be true for the sake of argument, what they're doing is actually what's prophecised so wouldn't work anyway.