Islam was founded in the seventh century when Muhammad, the Arab worlds greatest political and military leader went to Mecca and Medina. He had created the Quran from verses he claimed that he had been given by God. The Quran and the Hadith, the teachings and practices of Muhammad, are the two most holy books of Islam and Muhammad is venerated as the one true prophet.
In the Islamic world the Quran was and is accepted as the words of Allah as given to the Prophet. Given directly from Allah. Second in standing only to the Quran, the Hadith is esteemed as the Prophet's perfect understanding of the Quran. Both are said to be unalterable.
In other words, we are dealing with a religion that was founded around the year 622 and has not changed since. While most religions today are either intrinsically benign or have evolved into a non-acceptance of violence, Islam has never gone through any sort of reformation.
I give you some verses from the Quran:
Qur'an 5:33 - Murder (Punished, crucified for objecting to Sharia!)
"The punishment of those who wage war against Allah and His messenger and strive to make mischief in the land is only this, that they should be murdered or crucified or their hands and their feet should be cut off on opposite sides or they should be imprisoned; this shall be as a disgrace for them in this world, and in the hereafter they shall have a grievous chastisement"
Qur'an 9:29 - Dominate The World (Dhimmi / death / subdued!)
"Fight those who believe not in Allah nor the Last Day, nor hold that forbidden which hath been forbidden by Allah and His Messenger, nor acknowledge the religion of Truth, (even if they are) of the People of the Book (Jews and Christians), until they pay the Jizyah with willing submission, and feel themselves subdued."
Qur'an 9:73 - Apostates & Hypocrites (Non-Muslims are to be hunted like animals!)
"O Prophet! strive hard against the unbelievers and the hypocrites and be unyielding to them; and their abode is hell, and evil is the destination."
Harsh language. This is but a small sample. There is much more. I remind you that these are accepted as the true and immutable words of Allah.
The "sins" against Allah that provokes such vile, hate filled, and violent reactions in those profanely violent young people that think them selves believers are words and drawings. "Sins" of the pen. The Islamic cure is the cure of the AK47.
In this day and age civilized people, when aggrieved, write a strongly worded letters. Or sue. Or picket. But they don't draw down and kill a bunch of innocents. That type of behavior is so seventh century.