My theory on why they hate nukes so much: Quantum entanglement. Your soul, spirit, consciuosness or whatever you want to call it has mass; 21 grams to be exact. That consciousness is linked to something elsewhere via quantum entanglement (its a real, scientific, proven in a lab reality). Assuming that we really know nothing about anything since at best our intellect is less than 100 years old - I can only guess that nukes kill/destroy our consciusness AND whatever it's entangled to. Yes, that's bad for the souls lost but it's also bad for whatever/wherever they're linked to.

Smash atom here, smash atom in other universe, other reality, other timeline, other dimension or worse. Its like pulling the thread on a sweater. Something seemingly isolated causes something much larger to come unraveled. So in order to prevent catastrophic consequences we don't understand, they stop it.