Two other thoughts:
1) Christianity grew up and flourished with a heritage of Graeco-Roman thought, much of wich was democratic or republican. And depite ancient and medieval religious and political hierarchies, there were frequently votes taken amongst peers (e.g., ecumenical councils, or lords petitioning a king). Islam does not have such a heritage.
2) Christianity grew up and flourished with a heritage of Graeco-Roman self-criticism. In every age there were outlets for critiques of leaders' policies as well as examination of consciences by individuals. Self-doubt and self-criticism is a Western mainstay which has no counterpart in Islam.
examinations of conscience by individuals