That’s a harder question to answer and depends more on your own moral compass. Do you believe that having better defensive capabilities empowers the users of your creation to feel safe enough to do evil things? I certainly don’t think you could absolve the makers of anti-missile systems who supply militaries that are committing genocide.
Doesn’t make you any less responsible when the fruits of your labor are used to murder civilians.
What if I have only ever worked constructively on anti-missile defense systems?
That’s a harder question to answer and depends more on your own moral compass. Do you believe that having better defensive capabilities empowers the users of your creation to feel safe enough to do evil things? I certainly don’t think you could absolve the makers of anti-missile systems who supply militaries that are committing genocide.