>>81697472
>Then why are people willing to overcome their survival instinct in the name of ideology? Why do religious zealots show a complete willingness to kill their own children over perceived heresy?

Thinking too narrowly. That is itself a survival strategy, because it's about people putting the survival of their group or tribe above all else, engaging in self-sacrifice. The thing is that the're getting it all mangled up with superstition, but the drive is about the survival of the group they're in, which is because humans are social creatures living in social groups.