Some people are not able to distinguish the teachings of Islam from the behavior of Muslims. They think everything that a Muslim does is an Islamic teaching. The reality is not so. A Muslim may fall into error but there is no mistake in the teachings of Islam. A Muslim may do damage but Islam never orders to damage. If a person is willing to study Islam with a clear heart and mind, he will not meet unless the real truth, goodness and cleanliness.
There are so many truth and goodness contained in the Qur’an and the legally hadith. One of which can be founded in Surat Al-An’am verses 151-153. There Allah commands humans and jinn to avoid ten damages consisting of doing bad deeds to both parents, killing a child (or aborting a fetus) for fear of not being able to feed him, approaching the abominable act like adultery, carelessly killing people, abusing orphan’s property who are entrusted to us, cheat the scales, injustice to people who are close and distant to us, disobey all the commandments of God, and deviate from the religion of Allah (which has been taught by the Prophet and practiced by his companions).
Of these ten things Allah began with the most important one that is
قل تعالوا أتل ما حرم ربكم عليكم ألا تشركوا به شيء
“Say:” Come i will rehearse what Allah has (really) prohibited you from, join not anything as equal with Him. ”
Why assocciating Allah become the greatest prohibition?
Because of that damage and danger that will befall the perpetrators both in the world and the hereafter. If a heaten dies in a state of unrepentance then he will be eternal in hell; Not alive except for eternal torture. As in the world, associating Allah often bring humans to easily shed blood and various other vile acts. See how the behavior of pagans who worship idols. Each idol has its own priest, and each priest has its own teachings. Human slaughter or sacred prostitution are two things that are identical with pagan teachings. And the pagan doctrine certainly contained associating Allah.