All religions have fundamentalist because religion encourages people (obviously) to statically believe in its tenets and ways, which inevitably produces the very fundamentalist "moderate" religious people are trying so hard to portray as being "false" and not the "true" followers of their religion. It's a problem that's inevitable in the institutions.
Not all religions have been overrun by fundamentalists, and moderates have a voice in many religions. While it is true there are some fundamentalist religions where moderates don't have a voice, one just needs to look no further than the Catholic church with Pope Francis. He has breathed life into the faith and has more "moderate" views than many hard-core Catholics would prefer. But he is the church's leader, and he's bringing many moderates back into the church, which will do the Catholic faith good in the long run.