The question is then, are they worshiping God in a way he finds pleasing? Given that they treat Mohamed as infallible and think of heaven as a carnal pleasure land, I would say not.
You are free of course to argue that by trying to shape God to fit their image, they have in fact created a separate god. Which is a credible argument.
Islam was inspired by demonic vision intending to subvert and destroy the Torah, the Bible, and all who believe in them. It is diabolically and diametrically opposed to Jehovah and his Word.
Mohammed is a prophet of Lucifer.
It is far worse than you would make it appear. I suggest you read the Koran and accompanying hadiths to gain a better perspective. Pay special attention to prophecy in Islam as compared to the Hebrew Prophecy.