I fail to understand the reasoning of those religious extremists who are convinced that their belief system is the only valid one and everyone else is wrong. I assume that they do believe in an ultimate Creator, who created them as well as everyone and everything else which exists. In which case how can they justify their conviction that they are the only people who are correct? They must be convinced that they and only they know the mind of the Creator. To follow that logic means that they know as much as the Creator, so are equivalent to the Creator.
I think the description of that belief system is Blasphemy.