Sure, but that doesn't really help to justify killing them. Can I walk around and kill random people? I mean sooner or later they will all die for one reason or another, I am not really changing the outcome for anyone...
No, but the people in this case are not random, their death somehow saves billions, which means it very different from killing random people on the street.
In fact, we make far worse moral calculations than that frequently. Eg, if you've ever supported a war, you've agreed with killing completely innocent children, often in horrible ways, for the sake of whatever benefit the war might have had for the side you support. And there have been plenty wars fought for reasons other than self-defense. Take Iraq and Afghanistan for instance.
