Wars suck. But sometimes the result of not fighting a war sucks more. Sure, military projects could POTENTIALLY kill innocent civilians. But that's not a guarantee, modern Western militaries go out of their way to minimize that, and again sometimes the result of not fighting a war would cause even more innocent people to suffer or die.
The idea that "this one bad thing could happen, therefore I will do nothing that could remotely cause this one bad thing" is childish reasoning.
There are plenty of things that people can and do in private industry that are significantly more harmful than making some incremental improvement in a weapons platform.
The idea that "this one bad thing could happen, therefore I will do nothing that could remotely cause this one bad thing" is childish reasoning.