For those of us who know the truth, it is a ridiculous bit of grandstanding and buffoonery. However, I have no doubt that it plays well in the Middle East and has plenty of pious followers puffing out their chest in anticipation of the imminent victory of their faith.
The sad fact, however, is that this little "factoid" about the evil church suppressing the Gospel of Barnabas and covering up the fact that Jesus predicted the coming of Mohammed has been trotted out with amazing regularity for decades. Of course, the intent is clear. Keep the "us" versus "them" game going and constantly sling mud at the only monotheistic faith that could possibly compete with Islam.
In one respect, Muslims are no different from people anywhere. They are predisposed to believe any report that confirms what they already believe and will do no research to verify the authenticity of the claims being made.
Maybe the question for us today is what have we believed without conducting proper intellectual due diligence?