I've worked in defense, and I don't really see how it matters either way. If you're just a programmer, you have absolutely no control over how your creation is

I've worked in defense, and I don't really see how it matters either way. If you're just a programmer, you have absolutely no control over how your creation is used, and really not much control over what project you work on even (aside from picking and choosing your employer). Your own moral standards aren't going to affect anything as far as I can tell. I suppose if you refuse to work on, for instance, land mines because you think they should all be banned due to the effects they have long after a conflict is over, they'll just find someone else to do that work. This could be bad for your continued employment, but more likely they'll just move you to some other project you don't have such moral qualms with, because skilled engineers with a security clearance are hard to find and expensive to get a clearance for. Anyway, your own moral standards aren't somehow going to magically make your weapons system only useful for just causes.