Obviously, it's one thing to be a commander ordering an attack, vs a soldier firing the weapon, vs starting the company to make the weapon, vs being a supplier to the weapons company, vs being an employee at the manufacturer, etc.
What about working for a president who is going to inevitably order hundreds if not thousands murdered? Or voting for said president?
What about paying taxes, knowing those tax dollars will go to missiles and guns used to murder?
(This isn't a criticism of your worldview, by the way. I'm just genuinely curious about how others draw these lines.)