I've seen it specifically stated that it means "infidel" or "non-believer" - in Islam, we're led to believe... But in fact, Islam preaches respect for 'people of the book', except perhaps in it's most extreme (and MI-6/CIA supported) variants - like Takfiri, Wahhabi Jihadism.
Based upon his Templar Cross and "Deus Vult" tats, I would agree, that's where his head is at - Anti-Islamic bigotry.
Speaking of "burner"s... Zionist Empire Propaganda manager Jeffery Goldberg couldn't possibly have been included in their Signal War Crimes chat, by accident. I think the whole thing was deliberate, in order to shift the conversation from unlawful attacks on behalf of a foreign power (and in defense of their continuing Genocide of the Palestinians), and attacks upon Yemeni civilians - to a narrative about OPSEC, and competence, where the underlying questions are forever suppressed and ignored. Just my 2¢. Goldberg, an ALLEGEDLY REFORMED Kahanist, and a Zionist AbomiNationalist Asset, has been a goto-guy, for NeoCon Information Warfare strategies, for years.