I'm not budging. Neither is this reader:
"This usage is controversial. Islamists themselves may oppose the term because it suggests their philosophy to be a political extrapolation from Islam rather than a straightforward expression of Islam as a way of life."
Sounds a lot like the Reynolds-Althouse opposition to the use of Christianist. Regarding Prager, perhaps he should read the Constitution, Article VI, clause 3:
"The Senators and Representatives before mentioned, and the members of the several state legislatures, and all executive and judicial officers, both of the United States and of the several states, shall be bound by oath or affirmation, to support this Constitution; but no religious test shall ever be required as a qualification to any office or public trust under the United States."
What part of "no religious test" is unclear? I guess the Christianist part.