Believers consider it’s a virtue to be more religious and they believe that they will be rewarded "more" for being "more" holy. For this reason, they keep an open mind to Koran, accepting anything without questioning it. (Moreover, they are afraid to question Koran!)
Unfortunately, Koran is a book provoking violence and hinders rational thinking capacity. Islam put forwards so many rules and procedures that one has to follow which keep their mind fully occupied. For eg, one should enter the bathroom only with left leg and exit with the right leg, a prayer after you wake up, another when you first put your foot on the ground, followed by another for this, yet another for that - and for almost every activity there is a prayer and a particular way of doing it. They will be "rewarded" for doing these properly. This is really brain-washing in disguise. This never lets their rational mind to wake up.
They consider Mohammed to be the epitome of humanity and following his life and words ensures a path to the heaven. So, the more rewards you seek, the more you dwell into Koran, the more you agree with the acts of Mohammed and eventually one will be ready to die for their religion.
Ask any Isis people, and they will say they are just following the life and words of Prophet Mohammed. In other words, they are copying the life and acts of Prophet Mohammed.
I am not saying Isis and ones like those are clones or avatars of Prophet Mohammed, but they are the ones who show who was Prophet Mohammed to the non-Muslims. They show the reason why there are no other cultures co-existing with Islam peacefully. They are the ones who show the fate of other non-Islamic cultures in the event of Muslims gaining an upper hand in their population.
Please go through these post that questions the crux of Islamic beliefs. I hope you will find something interesting here:-