Let us not forget what happened when Caliph Umar took Egypt away from the Byzantine Empire as remembered by al-Qifti:
“As for the books you mention, if there is in it what complies with the Book of God [i.e. the Qur'an], then it is already there and is not needed...and if what is in these books contradict the Book of God there is no need for it. And you can then proceed in destroying them.”
This was worse than what the Christians did--in that books that affirmed the Qur'an were considered useless, and also slated for burning.
That is absolutely crazy. I first read of this in a book about Fermat and Wiles...