I think the fundamental difference here (so to speak) is that ISIS is not a fundamentalist uprising. Oh, sure, they claim to be a religious movement, but everyone in the region does. Fundamentalism, in any religion, is not typically accompanied by using sexual slavery as an incentive to get young men to fight for you (ISIS has quite the flexible and convenient moral code).
My understanding of ISIS (mostly from a Muslim Arab coworker, so of course my "expert" could be wrong) is that they're "religious" in the same way Scientology is: they have all the trappings of religion, but it's all quite contrived. They emphasize whatever parts of scripture helps their goals and ignore the rest in a very obvious and transparent way that fools almost no one. It's not that they're murdering "moderate Muslims" per se, they're simply murdering anyone who speaks up about how evil they are, or simply speaks against them, whether on religious grounds or any other grounds.
There are many other places in the world where IMO the problem really is religious fundamentalism, but those guys aren't raising armies and conquering vast territory. Even in Afghanistan it's just one tribe after another, not a united fundamentalist army.
I think it's a mistake to confuse the problem with fundamentalist Islam in other parts of the world and other cultures with ISIS and the Arabian Peninsula.