Did you intend this to be paradoxical?

A bit, yes. There's an inherent paradox in the argument about necessity. Put it another way: if the next technology turns all of your enemies into steam, but as a side effect, also does the same to their families, are you forced to develop it, because the people on the other side of the world will just get there first if you don't? What if the one after that is super low resource yet it also kills anyone who has ever shaken hands with your enemy? etc etc. I would argue that creating a new weapon, or developing existing ones further is not made more or less moral on the basis that your enemy might be doing it, because if you know your enemy's mind that well, you could easily defeat them using a slingshot.

This is likely wrong...Some of us would brutally murder each other with sticks and stones if they had nothing better.

Not sure I follow, this seems to be what I was saying. Read it back. The difference is that now we have technology capable of remotely erasing huge populations, and no means whatsoever of keeping it out of the hands of the freaks that invariably take power. It's therefore immoral to develop weapons because if you are clever enough to know how to do that, you should be clever enough to know how the resulting products will end up being used.

most defense work is not creating the atomic bomb. Most of it is incremental improvements

So the difference between them then is just one of scale. Oppenheimer probably never got a good night's sleep again in his life, but it's easy to persuade a thousand people to each do a thousandth of what he did. Then each person is only a thousandth as responsible as Oppenheimer. But each increment is still an evil deed, just a smaller one.
"Concern for man himself and his fate must always constitute the chief objective of all technological endeavors...in order that the creations of our mind shall be a blessing and not a curse to mankind. Never forget this in the midst of your diagrams and equations." People working on weapons are ignoring, forgetting or equivocating over this simple fact. Good people don't make bombs and sleep well at night. Find another job, where you can look back at your life's work and honestly believe you made the world a better place.

Anyway, we agree that psychopathic megalomaniacs are a feature of the human creature. And whether or not they are flying drones, driving tanks, or a leading a hoard of mounted Visigoths at your village, I think most of us would rather remove them as a threat from a safe distance... Like with a missile.

Most of us would prefer our enemies killed at range, without having to look then in the eye, sure. But look at what you're mixing up here: the psychopathic megalomaniacs who are sitting barking orders a world away from the lethality radii, and the grunts and (invariably) innocent collateral who are atomised inside them.