*If* they could establish a provenance for the "Gospel of Barnabas" in the 5th-6th century, that would mean it wasn't a 15th C. Islamic forgery, but yet-another heretical "gnostic gospel".
That would mean that the basic Muslim apologetic against Christianity is really the product of a cultic offshoot from Christianity, a heresy, which preceded Mohammed by maybe a century. And if it can be shown that Mohammed borrowed part of Islam from some Christian heresy, why not the whole thing? Suddenly he's not a prophet, just a plagiarist.
“Suddenly he’s not a prophet, just a plagiarist.”
The three “P’s” - Plagiarist, Pedophile, POS.
Just like the Dems in Congress and the Executive branch...
...they plagiarize The Communist Manifesto
...they are pedophiles, stealing the heritage that would be our children’s and our grandchildren’s
...and everyone of them is a POS