Let me ask another time, If You will call some FLDS member as "cristian"?

Jihadi Salafist are a totalitarian sect, they have no clue about Quran and no clue about the Shariah Law.
Telling "Allah Akbar" not made the dumb criminal acting against the Shariah Law as "muslim".
Just listen all the text of the letter if You are interested in argument.
There is enough data.

http://www.lettertobaghdadi.com/