In reality, there is often no particular consequences other than problems with their family, maybe. I know a lot of Muslims that converted to the Baha'i faith.
First thing about Islam:
- We believe there were prophets who received revelations from God.
- We believe the Qur'an is a revelation from God.
Believing scriptures are divinely inspired is a general thing in religion.......
I used to have a strange view when I was Christian. I believed those who believed in a Higher Power reached Him, while those who believed in nothing just rotted in the ground. Of course, I have different beliefs now. I think believing in the wrong god is better than believing in nothing.