The Quran, like many holy books, can be interpreted in many different ways. Plus, ISIL also refers to the Hadiths to justify many of their actions, and often times the Hadiths contradict the Quran
Here's me saying It's Koran when It's Quran. :S
Interesting. I've never heard of the Hadiths, what are they about?
EDIT: Nevermind: "The hadith literature is based on spoken reports that were in circulation in society after the death of Prophet Muhammad. Unlike the Quran itself, which was compiled under the official direction of the early Islamic State in Medina,[5] the hadith reports were not compiled by a central authority. Hadith were evaluated and gathered into large collections during the 8th and 9th centuries, generations after the death of Muhammad, after the end of the era of the "rightful" Rashidun Caliphate, over 1000 km from where Muhammad lived."
That's shaky ground to justify one's actions with.