The Qur'an is not the problem. The Old Testament is much nastier than The Qur'an. The problem is that while Christians perhaps never really had a hard-set belief in the word of The Bible and by the 15th Century Christianity had begun the great Reformation which made The Bible a spiritual guide rather than a book of law, that isn't the case with Islam. Arabs in the Middle East to this very day take the Qur'an to be the only reliable source of knowledge and the only needed source since it contains all knowledge. Even in moderate Islam (or as moderate as Islam gets) Muslims still look to the Qur'an as the moral authority before they look to their own common sense morality that most of us take for granted. At no point has the thought ever occurred to me that I need to check in a holy book to find out whether rape and murder are justifiable or not. And the Qur'an in several places, supported by the hadith, says yes, sometimes rape and murder are justifiable. That's why the moderates of Islam have a hard time criticizing Islamists and jihadists.
The hope would be that vast majority of moderates draw the line at putting words into the prophet's mouth that he didn't speak.. Or at least risk the conflict that would created if there was a larger more open debate about the more radical interpretations of Koran. Apparently -- they KNOW how rowdy and deadly that could become..
From what I have seen condemnation of Muslim extremists abusing the Koran is pretty widespread- it just doesn't get as much press as more extreme claims.
I am reading "Black Flag" right now on the origins of ISIS and the guys flocking to the extremist messages are not interested in what 'moderate muslims' thing- as far as they are concerned they are all apostates.