These states and elites with the access to the scary weapons ARE the ones doing the damage. The call is coming from inside the house.
I don't understand your point on nuclear proliferation concentrated in the hands of a few states preventing nuclear war or terrorism. Remember, the only two nuclear weapons used in attacks killed a quarter million people, ~90-95% civilians. By one of the few states who had the power. This is the definitional paradigm of state terrorism. And like, now look at the status quo of nuclear treaties and agreements and proliferation. Not exactly a success story.
It's obviously not worth personally formulating a "defense plan" for an AI-enabled bio attack were I personally to have access to SOA weights, but if history is any indication, I feel pretty confident that the likelihood of that happening remains far greater in the closed-weight, elite-state-access-only scenario than the open, democratized, and collectivized one.