So the threat is, "Give up the weapons that could kill millions of people, or we will kill millions of people." Oooookay, got it.
It was dry, but the funny bit, I think, is that Terran civilization can somehow get along without its billionaires.
Put aside the hereditary wealthy, whom I don't think you're thinking of, either. The existence of billionaires is an artifact of inefficient legal and economic systems, and the set of people who would work hard at whatever example you're thinking of for $billions but not for lesser, but still extreme, wealth is null.
Discuss.
If you think that a billion-dollar company can exist, then combining what we know about the inefficiency of committees with that fact we arrive at the conclusion that perhaps some people can reasonably be given control of billions as well.
Billionaires spend a small fraction of their money on superyachts and keep most of it invested which is the system working if you believe in it.
Some people use money to destroy or buy out their competitors. Some people use money to bribe or corrupt politicians and by extension to corrupt the entire democratic process. Some people use money to influence the media. And in these and many other ways, money can be used to make even more money in a runaway cycle without there being an efficient allocation of resources.
There are also a lot of harder-to-prove forms of political corruption, such as when a politician uses their power to benefit a company or industry, and then after retiring from politics they are given lucrative work with those same companies or in that industry. (And many many variations on this theme.)
Generally the law makers have made laws against Free agents (ie competitors) from colluding.
But in the event of a major war, and if it goes nuclear, biological or chemical, the billionaires can hole up on their yachts and ride it out in the relative safety of the middle of the ocean, just like the film Waterworld but less apocalyptic, so was the system working or is this why sanctions have been imposed? Its not like any of these billionaires can just take off now is it?