That's the conundrum Americans should all be thinking about.
Of course, there are a number of situations in which nuclear weapons could end up being used in the future (or very nearly were used in the past), but saying nuclear weapons should be completely dismantled by everyone is not as clearly desirable as you make it seem.
As noted up-thread how you choose to react is a personal issue. At a minimum complacency seems like an unwise response.
I've spent a good amount of time looking into the issue (for a number of reasons), and it seems to me that nuclear policy, on the level of an individual US citizen, is highly complex, especially if one concludes, as I have, that keeping nuclear weapons on some scale is the best option.
Then you need to basically move out of society. Every western country has provided funds to develop or employ some kind of military weapon that has led to the death of a civilian at some point. If you pay taxes or are not actively an anti-government anarchist then by default you are "contributing."
Whether you think your contribution is large enough to warrant complicity or not is just a matter of where you draw the line in your own head.
For example, the US is the only country in the world that openly conducts drone strikes on foreign territory for extrajudicial killings of political opponents. Not just in Afghanistan, but also in Yemen and a number of other countries.
To give another example, if a country uses chemical warfare agents against civilians, this is a clear-cut violation of international laws, treaties, and conventions. Moreover, the verdict of experts and international judges does count.
Although there is plenty of room for disagreement and legal procedure, as in any other legally and morally relevant matter, none of these issues are based on "an arbitrary line in my head" at all.
So yes, the line of demarcation between when you feel you are complicit with the "immoral" behavior is arbitrary and not based on any legal basis.
extrajudicial killings of political opponents
It's important to note that this is not true legally. It conflicts with EO 12333 [1] [2]. The targeting process for any airstrike (except in VERY rare cases like Op Neptune) goes through a very complex, legal de-confliction process in close coordination with local governments/militaries and is not done for political purposes. In this sense "political" is a term of art, not a statement about the philosophical position of a potential target.
I think the major problem here is the massive disparity with what the general public thinks they know about airstrikes in general and UAV strikes (aka drone) specifically. The general public has about 1/1000th of the information they need to understand it and how it actually happens in practice. The DoD is largely to blame for not being more explicit about this, but there are real concerns with security/secrecy.
[1] https://www.archives.gov/federal-register/codification/execu...
[2] https://www.law.upenn.edu/institutes/cerl/conferences/target...
My take on it is that if you contribute in any way to the development of a weapon that is used in morally unjustifiable ways, then you're complicit to murder and manslaughter, and you should be aware of that.
For example, the US is conducting drone strikes in Afghanistan, which are essentially political assassinations. These are condemned by almost any independent expert on international human rights and come with a very high death toll of civilians, including many women and children. In fact, the number of non-combatant civilian victims is routinely higher than the number of targets. Moreover, they are routinely conducted over the territory of another, sovereign country without any international mandate, without any judicial oversight, and without any trial.
If you participate in developing the drones or missiles that used in these strikes, or support them in any other way, then you are making yourself at least partially guilty of murder or manslaughter. From a moral perspective, it barely matters whether you believe or feel that the drone strikes keep your country safe. Extrajudicial killings of political opponents in foreign countries you are not at war with are illegal and immoral even if they have perceived or real positive side effects for your country.
That's just an example to illustrate that it matters a lot for which government you develop weapons and what track record your country has in terms of human rights, military aggressions against other countries or lack thereof, and so on. There's probably less of a problem if you develop weapons for the Swedish army than if you develop weapons for Russia or the US.
It also depends on the types of weapons, of course. Don't tell me it would be fine to develop chemical warfare agents, outlawed types of anti-person land mines, or autonomous killer robots, because they would 'keep your country safe'. Some technologies are just despicable. There's a reason why lasers that blind soldiers on the battlefield are outlawed.