When a religion will tolerate no criticism of itself (Islam, Scientology) it is an indication that the leaders know that their religion cannot stand tall in the light of day.
I submit that Islam is not a religion as usually defined. It is an invasive totalitarian governmental system with laws known as sharia. The religious structure is part of the enforcement wing of the system.
The religious trappings give obvious advantages to the system as it metastasizes within a society. It's goal is a world living under sharia law.