It escapes you? Defense against another nation of course. You have a god-given right, as a peaceful person minding your own business, to defend yourself against an aggressor nation. Likewise, if someday Musk has a five year old child that wants to be able to defend his/herself against an aggressor nation, they have a right to nukes just the same, as long as they can afford it. The only hurdle to attaining arms, should be a person's own effort, because if you have the money, it shouldn't matter if you're five, deemed "insane" by an oppressor gov't institution, or even if you're a serial killer.I'm not a fan of nuclear weapons, but that doesn't grant me the right to then delegate that nonexistent right to government to keep you from having one. Why anyone would want one, unless they were psychotic, escapes me. Nuclear weapons are indiscriminate killers and are hard to justify as "defensive weapons" when they are used. If there were no nation state tax farms, I doubt nuclear weapons would be an issue.
As an aside, what would realistically stop crony capitalists like Bezo's, Gates or Musk from getting nukes even in the present governmental structure if they really wanted them ? They got the money.