While it's a relevant point, the risk (in a probability * cost sense, to address your point about terrorists using a nuclear/radiological weapon were one availa

While it's a relevant point, the risk (in a probability * cost sense, to address your point about terrorists using a nuclear/radiological weapon were one available) of terrorism has to be addressed somehow or you're cherry picking one from a number of extremely rare but potentially catastrophic events to worry about. We're not spending trillions of dollars and thousands of lives on a War on Giant Asteroids, for example.