Your hill is one of many
When I write about Christianity, it is from the vantage of being raised in it and living with it all around, both Catholic and protestant, from Cooneyite to Maronite. I know that most sects hold a range of adherents, from liberal to fundamentalist. I have a feel for how US politics overlays religion, for example, that Catholic social teaching is more liberal, as measured by the US spectrum, and quite different from what you find in, say, Assemblies of God. I know belief in the pews departs quite a bit from what is preached from the pulpit. I know I can’t point to some Deuteronomical law and insist that Christians must believe in it, because most don’t. Their explanation of that may make no sense, but the fact of it remains. I know the Catholic Church includes an established procedure for defining official doctrine, while Baptists officially view what comes out of their conventions quite differently from that. I would love to see a survey on how seriously any of that is taken in the pews. I know that the protestants who preach dispensationalism (the rapture and tribulation, etc.) mostly have no clue who created that doctrine.
Because of this background knowledge, I can write about Christianity — at least the American varieties — and hope I don’t make largely wrong characterizations. Someone from some part of the world where Christianity is scarce, who never learned much about it, wouldn’t be as familiar with the warp and weft of its various sects. They might wrongly think fundamentalists would all avoid shrimp and polyester-blend shirts. Or be surprised to learn that Pope Francis believes in demon-possession and exorcism. Or not realize that the religion is large enough to hold both fire-breathing fundamentalists who think most everyone is going to hell, gays leading the way, and liberal universalists who happily watch their lesbian pastor officiate over two men getting married.
I am not as familiar with the Islamic world, knowing only the coarse outlines of its sects, the difference between a twelver and a sevener only something I once read about in college history. I know both Saudi Arabia and Indonesia are Sunni, but suspect that’s much like saying that the Church of England and Assemblies of God are both protestant. Because I know so much less about the religious landscape of the former than I do the latter, I have to be more cautious in writing about Muslims. There is a large error in thinking that comes from seeing the multi-varied hues of those nearby, while lumping those more distant — geographically or ideologically — into coarse categories. This happens even in national politics. Some Americans on the right seem unable to distinguish liberals from socialists, and are wholly ignorant of all arguments that don’t take place on the right. Some on the left incorrectly view every expression of right-wing politics as originating in corporate interest.
Avicenna, a former-Hindu, now atheist medical student, has written an excellent post on how this kind of error leads to Islamophobia, and how that is different from legitimate criticism of Islam.