He writes: "Say there is country A who conquers countries B, C, & D, imposing external costs on country Z, and even threatening large future costs (e.g. an invasion). It may make sense for country Z to increase war spending to organize a way of reducing total future costs by preemptively eliminating A’s capacity to impose costs on Z. That doesn’t necessarily mean that Z’s war spending creates a net benefit, it just mitigates the loss."
I guess health care spending doesn't involve a net benefit either! That is just mitigating a loss - my eventual breakage and death.
Of course what's really at issue here is how we're netting things out. I can't control what A does. So I take it as given. When I assess net benefits it's going to be based on the consequences of my decision.