It's the arms race itself (and the fact that we allow it to continue) that's immoral. Acting rationally within the arms race is not immoral. Our laws should address the core causes of this arms race.

People are starting to wake up to the notion of "systemic issues," but still too slow to apply what they've learned about that topic to other matters. It's a mistake to focus on the behavior of individuals in a system that's sanctioning and encouraging bad behavior.