Well, it certainly is "critical", but I don't see much "history" here. Saying that Islam is simply Christianity corrupted by Satan ignores the real historical roots of Islam.
There were both Christians (of various groups) and Jews in 7th century Arabia. But the greater influence on Mohammad seems to have been Sabaeanism/Mandaeanism, which in turn was influenced, and perhaps evolved from, the Ebionites, which in turn emerged from Essene Judaism. There was no single organized movement, but rather a lot of closely related groups. Some traced their spiritual ancestry to John the Baptist. Others believed that Jesus was a prophet or the messiah, but did not believe in his divinity, and rejected trinitarianism.
Even before the bar Kochba rebellion was quashed in 135 C.E., these groups had been moving east. Ebionite Christianity became increasingly marginalized and was finally declared heretical by the hellenic Christian churches.
Some of the elements of these groups included:
• emphasis on purity (practicing frequent, even daily, "baptism")
• eating kosher food or vegetarianism
• belief in a "Righteous Teacher" or Teachers, who will return
• strict unitarian monotheism
• messianic and apocalyptic worldview
• in later times, they believed that the scriptures had been corrupted, and thus had their own "corrected" version
• believed Jesus was a prophet or the messiah
• theocratic, and often willing to use violence to impose God's Law
It doesn't take too much imagination to see how many of these elements were absorbed into Islam. This is particularly true of Shi'ism, which to this day teaches a doctrine of the "hidden Imam" with clear connections to Essene teachings about the first or primal Adam (remember the 90' tall Adam?) and Tzaddikim or Righteous Teachers.
Allah was known to the pre-Islamic . . . Arabs; he was one of the Meccan deities
"Allah" is simply the Arabic word for "God". Arabic Christians use that name to refer to the trinitarian God of Christianity, with no suggestion that this refers to some pagan moon god. You could just as easily make the case that trinitarian Christianity coopted some of the language of hellenistic paganism and mystery religion. The fact that some of the same language is used does not mean that, for example, you equate Jesus with Adonis or Mithra. Whatever polytheistic elements there were in early Islam were quickly purged.
There is plenty to disagree with about Islam -- the superstition and immorality the article discusses, for example -- without bringing in the whole "moon god" thing.
The supernatural death and resurrection of Messiah on a cross is rooted in reality, and by witnesses, and is corroborated even by secular history.
Huh? I don't really think secular history corroborates the resurrection of Jesus.