You're quite right. And not only the Koran. Mohammad's own example as recorded in the Hadiths is horribly instructive: his collection of slave-concubines, including a Jewish woman who was forced to watch her husband being beheaded, and then claimed by Mohammad for his harem; and his consummation of marriage with his child-bride Aisha (married at age 6, consummated at age 9, when Mohammad was 54) -- what disgusting things for a so-called prophet to do.
When the teachings of a group allow for such barbarism, there comes a time when the group itself has to be held accountable. Obviously not all Muslims are barbarians, in fact the overwhelming majority are not; however, very few Muslims (especially in the areas of the world that are predominantly Muslim) are willing to denounce those portions of the Koran that condone actions such as these.
It is not unlike Eisenhower forcing the citizens of nearby towns to view the concentration camps, the fact that they were not participants did not excuse their passive assent.