Honestly it's hard to write a response because it's such flagrant nonsense I don't really know what to say.
Christian priests and monks wrote a lot of history, true, but the idea that there was a coherent policy behind this is incredibly anachronistic. The Catholic church didn't have anything near the coherence to administer religious policy across Europe until at the EARLIEST the 11th and 12th centuries, and things don't really start rolling until 4th Lateran in 1215, and even then the Catholic church simply never had the authority, power and agreement to pull off some sort of centuries long deception this article describes.
Constantinople was not a "Tributary" of Baghdad under the Abbasids, I don't know what they're talking about. The Byzantine Empire remained a coherent, powerful, and effective polity until the late 12th/Early 13th Century, and the Nicean Empire remained a local power for some time after. Certainly, the empire suffered serious reverses during the Arab Conquests in the 7th Century, but they recovered, and continued to exist as a major independent power for centuries.
I don't even know what to do about the Greek stuff. Loads of Greek works have been transmitted through either Latin Christian or Byzantine worlds, without coming through Islamic hands at all. Boethius, a 5th century Roman author, was heavily and obviously influenced by Greek Philosophy, and he is quoted extensively by Medieval Authors. Islamic authors wrote commentaries on Greek works.There is literally 0 evidence for anything the author saying, and frankly I don't know where he got any of it. I'm not even going to bother with the bits on mathematics, I'm not interested enough to care, except to note that Greek mathematics was largely based on geometry, and therefore didn't have much need for a numbering system. This is of course setting aside the tons of manuscript fragments (and I believe a few largely complete ones, though I'm not a classicist) that were found in modern times and date to antiquity, and predate Islam.
Of course, Christian authors had a particular perspective on things that caused them to distort facts sometimes. So does EVERYONE ELSE. This is surprising to absolutely no one. It is, in fact, one of the primary jobs of the historian to consider the potential biases and perspectives of each author, to cross check with all of the other available evidence, and come to a conclusion. That is, however, not what this article does. It aggressively makes up, misinterprets or distorts facts. To give him a taste of his own suggested medicine, going by the Author's past works, he appears to be some sort of Indian nationalist, who wants to discredit "The West" (That seemingly eternal, ridiculous construct) for political reasons. Whatever your feelings on that endeavor, however, it hasn't given him much insight into Medieval History.
TLDR: Totally bankrupt of anything approaching accuracy.