There is an undeniable conflict between "Don't be evil." and "Evil pays.". A lot of what militaries do can be best described as the lesser of two evils. Murdering people is bad, but sometimes a little murder can prevent a lot of murder. However ethically or unethically a state uses force, there's usually a lot of money to be had in supplying that state with the means of force.

Is there room for ethics in military research and procurement? Absolutely. An AI company might say, "We will help you choose the best targets when under time pressure, but we won't provide an oracle that lets you justify indiscriminate killing of civilians." An explosives factory might say, "We'll build precision missile warheads for you, but not white phosphorous or cluster munitions, because these kill civilians indiscriminately.". People working for companies that do defence work have a moral obligation to observe how their labour is used and refuse to give it if the results are unethical. It's no different from soldiers having a moral duty to refuse illegal orders.

To answer your question, I'd say that participating in the defence industry can be justifiable if you remain guided by ethics, and unjustifiable if you abandon them for money. e.g. If you're currently doing anything to help develop the IDF's Lavender or "Where's Daddy" programs, it's pretty hard to argue that you have a functioning moral compass.

It's also completely fine to say, "I don't want to deal with moral grey zones" and refuse to work for companies that do military work. You might make less money, but you'll almost certainly sleep easier.

No need to get serious. Only a sith deals in absolutes. There's plenty of work within the us military that is definitely not evil. Even within the field of weapons development. You could say develop a target selection approach that is less likely to blow up a school halfway across the world than existing approaches. You are literally saving lives working on that project, despite what the people who only see in black and white and make grandstand positions online might think.

I think it’s difficult to come up with hard and fast rules. But the fact that the US government (falsely) renamed their Department of Defense to Department of War is perhaps a useful signal.

I think this is secondary to a widespread loss of confidence in our nation's political and foreign policy apparatus to do what's right for the average American. "Working for the military is evil" descends from a post-Vietnam, post-Iraq, post-Snowden worldview that presupposes that the military will leverage technology it has access to in unexpected, undesirable, and broadly harmful ways.

> * Or is the argument that it's only US companies which shouldn't, because the* US is uniquely evil?

What are the (current?) foreign policy goals of the country in question? If it leans more defensive, like Japan, that's different than a country that may have a more interventionist bent.

Also what product(s) is the company developing or offering (field hospital equipment or are we talking about Palantir)?

Other countries probably focus quite a bit more on the defense aspect. How many times has the US military countered a hostile attacking force? Instead, I can think of significantly more instances where the US was instigating the situation.

If your country's defense department is conducting itself ethically, and the contracts are for equipment or technology that is not inherently ethically fraught (like autonymous weapon systems), then one might consider that acceptable if you aren't a pacifist. An enormous amount of US military technology and weapons have been recently used to perpetuate a genocide, so the US is certainly an outlier in the global landscape.

Work for defense but elect better leaders. Your leaders decide where and when the military is used.

There's a class of people in the West who have forgotten that wars happen and that defense is necessary. American especially benefit from two oceans separating them from the rest of the world and having never seen a war except on CNN.

Some of them, esp in central/eastern Europe, were rudely woken up in 2022 when Russian tanks rolle into a neighboring country. Others still have their heads buried in the sand and will not wake up even when Chinese robots march in Taipei in a few years.