I'm the sort who asks. Many who answered just didn't think it through, they didn't think about what the thing they were working on actually did within the larger system. I won't generalize this to the whole population (why I won't claim it's the majority of all people in the field) but the majority I did discuss this with had, at best, a hand-wavey "national defense" justification but did not think about what the thing they worked on did. Its effectiveness for its job, or its ultimate purpose.

Though a lot actually just wouldn't even discuss it in the first place. I think, though, that if you're going to work on a weapon or a component for a weapon you owe it to yourself to think deeply about the topic. I've known too many people who thought about it too late and realized that they couldn't live with it. Better to figure that out at the start and change career paths than at the end and either kill yourself or drink yourself to death.