“On the contrary, there are many papal and saintly quotes throughout Church history that are very clear that Islam is a diabolical sect (ie. worship Satan)...”
Actually, I don’t think any of the quotes you linked to say Muslims worship the Devil - although I freely admit I read only the comments in bold. A “diabolical sect” is one started by the Devil or oriented to serving his purposes. It’s purpose is not necessarily to directly worship the Devil, however, but to subtract from the Body of Christ and oppose it as a counterfeit. The very use of the word “sect” helps make that clear. That’s why Islam is so successful as an opponent of Christianity. It kept many of the words and ideas of Judaism and Christianity but it denies the very essence of Christian theology - the existence of the Trinity .
So, a diabolical sect, started by the Devil can still bring about worship of the true God? Why would the Devil wish to start a sect that would result in the worship of the true God rather than himself?
I think it is important to take all of those quotes together. Together, they certainly do not support the error that Muslims worship the same God as we do.
I think that certain Muslims think they worship the one True God, but they do not. The devil started their religion and it is he who gets the glory in that religion.