It's hardly a silly question.
From the article itself:
In the milieu in which the Quran arose, there was a widespread practice of men having sexual relationships with unfree women, said Kecia Ali, an associate professor of religion at Boston University and the author of a book on slavery in early Islam. It wasnt a particular religious institution. It was just how people did things.
Cole Bunzel, a scholar of Islamic theology at Princeton University, disagrees, pointing to the numerous references to the phrase Those your right hand possesses in the Quran, which for centuries has been interpreted to mean female slaves. He also points to the corpus of Islamic jurisprudence, which continues into the modern era and which he says includes detailed rules for the treatment of slaves.
There is a great deal of scripture that sanctions slavery, said Mr. Bunzel, the author of a research paper published by the Brookings Institution on the ideology of the Islamic State. You can argue that it is no longer relevant and has fallen into abeyance. ISIS would argue that these institutions need to be revived, because that is what the Prophet and his companions did.
