> I haven't prescribed what would happen to the money, simply that the rich need to take a haircut to make things more even
Ah, we've reached the crux of the problem. You are not concerned with making things good only with making them even. This is just crab mentality[1]. Someone else has more than you, so you need to pull them down. Or perhaps you've conflated the two and think that if things are even, they will necessarily be good, or at least better than they are when they're uneven. Let me assure you, it is entirely possible for things to become more even and also have everyone be worse off than they were before.
> If you also pursue a more robust, less concentrated economy more generally, you could certainly invest the money in entrepreneurship, small farms, improved IT infrastructure, etc., etc.
Sure, we can invest in those things. We can also pursue policies (like antitrust enforcement) that would naturally result in less inequality without distorting the market by confiscating and destroying wealth when it reaches some arbitrary number.
> Won't somebody please think of the poor billionaire!
I stated early on that Bezos and other billionaires would be the people least hurt by what you're proposing. They're not who I'm concerned about. Bezos doesn't have $180,000,000,000 or however much he's currently worth. He has shares representing about 13% of Amazon. Now they're worth that much. Ten years ago they were worth a lot less. 20 years ago they were practically worthless. It's the same shares. The market just collectively decided they're worth a lot more now. He didn't take anything from you, do you see?
It's not clear when you're proposing that his shares should only be worth $50B instead of $180B whether that you mean you want to take away a portion of them, or just limit how much they can be worth, or what. Generally stocks are priced based on how much money investors think the company will make in the future. In the aggregate, the price of the stock market overall is our belief in how well the economy will do in the future. When you propose that the value of this should be limited, you're proposing that the economy - everyone - should be collectively poorer in the future. This does happen sometimes, we call it recessions, depressions, etc. It generally does not bode well for the poorest people (billionaires are usually fine though).
But hey, who cares if we're all poor right? As long as nobody has any more than anybody else it must necessarily be good.
> Again, we've done this kind of thing before, and the billionaires and their defenders ho-hummed the same tune, and all that happened was the emergence of the middle class and fairly broad economic prosperity.
It's true the New Deal happened and then a strong middle class emerged some years later, that doesn't mean one caused the other. There was a little thing called World War II as well, and the rest of the productive capacity of the industrial world being destroyed with only America left may have contributed to the abundance of high-paying manufacturing jobs, just a little.
> FWIW, there is historical precedent for passing a tax law targeting the single richest person in the country (John D. Rockerfeller at the time).
Yeah, there's a historical precedent for burning witches at the stake too, that doesn't mean it's a good thing.
[1] https://en.wikipedia.org/wiki/Crab_mentality