It has been difficult to devise an adequate descriptor for the horrific behavior of those who justify their actions with the cloak of religion. Wisely, President Obama refuses to be trapped into using the 'Islamic Terrorism' meme, because the terrorost community will use that characterization as 'proof' that this is the Crusader Era all over again.
So I would suggest the phrase 'Faith Traitors' to describe radicals of all allegedly 'religious' terrorists. Traitor has an ugly connotation across all cultures and a Faith Traitor, one who usurps a legitimate tradition for horrific purposes, must be despised. Better still, the phrase is universal; fundamentalist Christians, bombing clinics in the name of their religion are Faith Traitors. KKK members justifying racism, murder, discrimination in the name of Christianity are likewise Faith Traitors, co-opting the philosophy of the larger community to their own narrow, traitorous goals.
The president was not wrong when he encouraged Americans to understand that the Faith Traitor persona is not limited to those who live far away and practice a different religion. They are here among us, as well, and should be identified as such.