Some Protestant Christians are coming up with the argument that Islam was created by the Catholics. They are suggesting that the wife of Prophet Muhammad (peace be upon him) was a Catholic nun and her cousin Waraqa bin Nawfal a Catholic monk both were influencing what Muhammad taught.
Answer to the Protestant claim:
"They desire to extinguish Allah's Light with their mouths, but Allah will perfect His Light, though the unbelievers hate it. He sent His Messenger with guidance and the Religion of Truth to exalt it over every other religion, though the idolaters hate it." (Surat as-Saff: 8-9)
There are some people who are promoting the idea that Islam was "invented" by Catholics.
As to the validity of this idea, I don't know where to begin. Let me start by saying that we should never believe something just because someone says it. People have been trying to explain away Islam for more than 1400 years. This argument that Islam was created by the Catholic Church, is just another example of people trying to make sense of Islam's origins and coming to the wrong conclusion. People simply cannot fathom the possibility that it (Islam) is in fact from God, the Creator of the Heavens and the Earth.
There are some people who will say anything to malign Islam and the source from which it came. This claim is no different. The idea that Khadija was a 'Catholic nun' is laughable, silly and ludicrous. There is not a shred of evidence to support this claim. And the idea that her cousin, Waraqa bin Nawfal was a Catholic who was behind the prophethood of Muhammad is completely baseless, without a shred of historical evidence.
Here are the undeniable facts: Khadijah was never a Catholic and never a nun. She was a non-idol-worshipping Arab, who was born into a wealthy family. She inherited her father's lucrative trading business, and continued that business upon his death. She hired Muhammad to conduct her trade, grew fond of his character and trustworthiness, and eventually proposed to him.
Her cousin Waraqa bin Nawfal, was a monk who believed and worshipped the One and only True God, the Creator. He was familiar with Scripture and lived the life of a servant to his Creator. When Muhammad began to receive revelation, Waraqa confirmed the source of the revelation upon hearing what the Prophet had experienced. He said, "This is like the message that was revealed to Moses. I wish I were young. I wish I could be alive when your people drive you out." Muhammad replied, "Will my people drive me out?" Waraqa said, "Yes, for no man has come with what you have brought, but was opposed. If I were to live during your era, I would give you great support." Days later, Waraqa passed away (Islam was revealed over the course of 23 years).
So the basis of this lie has no merit. The enemies of Islam, the idol-worshippers threw everything that had against Muhammad during his lifetime, but they never said Islam was plagiarized from Christianity, or Catholicism. It is a modern invention, with no merit whatsoever.