Is it because they are completely ignorant of pre-Islamic Arabian society (especially around the birth of Muhammad), or is it just because they are substituting doctrine for history?
Well in history during my school days we were taught Judaism got going about 4000 years ago, Christianity 2000 years ago and Islam in the 6th century about 1500 years ago. Do the math.
Islam is the most Monotheist religion out there as for Pre - Islamic Arabian Society.. Arabs are cousins of Hebrews.. i.e. Children of Israel .. if you know ..
Religion of Abraham is the right religion which is Islam .. Peace
Its the religion which came into existence as men set foot on earth. Even Hindu Scriptures which are the OLDEST which preach MONOTHEISM .. and prophecise the coming of the Final Prophet in VEDAS is clear evidence that Prophet Muhammad PBUH is the last and final messenger of GOD..
Prophet is also prophecized in Torah and Gospel(injeel).. Peace
God says in Quran:-
And thus We have SENT to YOU (O Muhammad) a Revelation, and a Mercy) of Our Command. YOU KNEW NOT what is the BOOK, nor what is FAITH? But We have made it (this Qur'an) a light wherewith We guide whosoever of Our slaves We will. And verily, YOU (O Muhammad) are indeed guiding (mankind) to the STRAIGHT PATH (Monotheism).
( ???? ?????? , Ash-Shura, Chapter #42, Verse #52)
In English, "Islam" means "religion that follows the teachings of Mohammad". Naturally, as Mohammad was active in the 7th century C.E., it is not possible that this "Islam" predates Christianity.
In Arabic, "Islam" means "submission [to God]", and **according to Islamic teaching** Adam, Abraham, Moses and others all practiced proper "Islam". Understand: in Arabic (and, therefore, in the Islamic religion), "Islam" does NOT have the same meaning as it does in English.
I think most Jewish and Christian people will agree that Abraham and Moses practiced proper submission to God. This submission is not the English word "Islam" - but it certainly is hard to deny that Abraham and Moses practiced proper submission to God, a practice that in Arabic is referred to as "Islam".
The argument that they are "substituting doctrine for history" may be valid. However, the linguistic reality is that in Arabic and in the Muslim religion "Islam" means "submission [to God]". When discussing such issues with Muslims using the English language, it is important to specify that you are using the English definition of "Islam" to avoid confusion (because they are likely to be using the Arabic definition as taught by their religion).
Nobody who isn't a Muslim. It's a nonsensical case of retconning done by a syncretic mythology to explain why it is more valid than the faiths it is primarily based upon.