Very true. Incidentally (and ironically), Islamically one is not allowed to overthrow their (Muslim) government to "establish a caliphate". So what ISIS is doing is against the teachings of Islam to start with. They take texts, keep what they like and leave out what they don't like, and use those texts for their own purpose.
We have in Islamic literature, several authentic narrations that talk about, and warn of people who have a similar ideology to that of ISIS.