To me, the salient point of that analogy is that the engineer designed execution chambers for Nazis. The engineers who designed the Sherman tank, the Garand rifle, or the Spitfire fighter plane also built weapons, weapons that killed people, but the judgment of history is that those people needed to be killed and thank God for the engineers who made that possible.

So, there are two aspects of that: first, do you trust the people you're designing a weapon for to use it for justifiable purposes, and second, how does the weapon itself influence whether it can be used for just or unjust reasons? Gas chambers, for example, can only be used to kill someone whom you are already able to coerce into entering it; its only use is to murder a helpless prisoner. A Spitfire or Hurricane can shoot down bombers but not necessarily do that much damage on the ground. Orwell had an interesting perspective on this question: "Thus, for example, tanks, battleships and bombing planes are inherently tyrannical weapons, while rifles, muskets, long-bows, and hand-grenades are inherently democratic weapons. A complex weapon makes the strong stronger, while a simple weapon — so long as there is no answer to it — gives claws to the weak."

I really don't have answers. The stance of, "weapons equals bad, therefore it's wrong to ever help design weapons" is a pacifist notion, and maybe that appeals to you, but if you're not a pacifist, it becomes a complicated question with certain political ramifications.