St. John Bosco on Mohammedanism
Regarding Idolatry, I think there is no need to discuss this with you, since nowadays it does not exist, with the exception of very few countries where the light of the Gospel has still not penetrated.
F. Mohammedanism is a collection of maxims extracted from various religions, which, if practiced, bring about the destruction of every moral principle.
S. Who started Mohammedanism?
In the year 570, Mohamed was born into a poor family, of a Jewish mother and gentile father, in Mecca an Arabian city not far from the Red Sea. In search of glory and desirous of bettering his conditions, he wandered around several countries and managed in Damascus to become the agent of a merchant’s widow who afterwards married him. He was cunning enough to take advantage of his infirmities as well as her ignorance, to establish a religion. Suffering from epilepsy, male caduco, he claimed his frequent falls were ecstasies wherein he had conversations with the Angel Gabriel.
S. What an imposter to deceive people like that! Did he also try to work miracles to support his predication?
With all of this he claimed to have worked one miracle. He said he had been able to restore a piece of the moon after it had fallen onto his sleeve; to commemorate this ridiculous miracle, the Muslims made the half-moon their emblem.
You laugh, beloved sons, and you are right to do so, since a man of that sort [simply] had to be deemed a charlatan, not the predicator of a new religion. For this reason, his fellow-citizens wanted to imprison him and put him to death since his reputation as an imposter and disturber of the peace was widely known. But he managed to escape and retreated to the city of Medina along with some libertines who helped him and made him the ruler of that city. 
S. What exactly does the Mohammedan religion consist of?
F. Since the peoples of Arabia were in part Jews, Christians and Pagans, he consequently selected a part of the religion they professed in order to induce them to follow him, choosing in particular, those points that would favor sensual pleasures the most.
S. Mohamed must have been an erudite man?
F. Absolutely not, he couldn’t even write; and in composing his Qur’an he was assisted by a Jew and an apostate monk. When discussing things contained in Holy Scripture he confused the facts; for example, he attributes to Mary, Moses’ sister, many facts that regard Mary, the Mother of Jesus Christ, in addition to many, many other frightful errors.
S. This seems hard to believe: if Mohamed was ignorant and he didn’t work any miracles how could he have propagated his religion?
S. What a villain! This cannot be the way to convert people! Without doubt, Mohamed being such an ignoramus must have planted many seeds of error in the Qur’an?
F. We could say the Koran is a series of errors, the most enormous ones being against morality and the worship of the true God. For example, it excuses from sin those who deny God out of fear of death; it permits revenge; it guarantees its followers a Paradise filled only of earthly pleasures. In short, this false prophet’s doctrine permits things so obscene, that the Christian soul is horrified just naming them.
F. The difference is very great. Mohamed established his religion with violence and arms; Jesus Christ established His Church with words of peace using His poor disciples. Mohamed incited the passions; Jesus Christ commanded the denial of self. Mohamed worked no miracles; Jesus Christ worked uncountable miracles in broad daylight and in the presence of countless multitudes. Mohamed’s doctrines are ridiculous, immoral and corrupting; Jesus Christ’s are august, sublime and pure. In Mohamed not even one prophecy was fulfilled; in Jesus Christ all were.
Taken from: On Islam from “IL CATTOLICO, ISTRUITO NELLA SUA RELIGIONE, TRATTENIMENTI ( Torino 1853). [The Catholic educated in his religion. Conversations with the Father of a Family and his beloved sons, in relation to the needs of the present day. Summarized by Giovanni Bosco, priest. (Turin, 1853)].