Is fundamentalism within any religion a dangerous thing?
Belief of any sort that places the soul of the person in peril of eternal damnation, apart from God, is dangerous to the maximum extent. Religion is faith in a system of belief. Christianity is belief in a Person --Jesus Christ. Belief in Him is the only way to Heaven and God the Father following physical life on Planet Earth. The Bible tells us:
"Jesus saith unto him, I am the way, the truth, and the life: no man cometh unto the Father, but by me" (John 14:6).
To reject Jesus is to miss Heaven and God the Father for all eternity. It means, instead, spending eternity in the Lake of Fire because of unforgiven sin.
Jesus proclaimed about himself:
"For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life. For God sent not his Son into the world to condemn the world; but that the world through him might be saved. He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God" (John 3:16-18).
All religion is dangerous. Jesus is the only One in whom is peace and safety.