If they're true (read: have sufficiently good reasons to believe them), then it's not extreme to live in accordance with them. In fact, it is arguably insane not to live in accordance with them. Imagine if someone said "Oh, I believe things fall to the ground when dropped, but I'm not an extremist about it". What does that mean?? That you only sort of believe that they fall to the ground? That you only sometimes avoid jumping off of bridges?
If they're somewhat true, then they need refinement and correction because they contain error.
If they're false, then it would be an error to follow them in any way.
So really, if what's being done is evil or wrong, it should maybe be called religious error, or just error.