The entire point of the article is about taxing the wealth of extremely rich people rather than income because the wealth is structured to not generate taxable

The entire point of the article is about taxing the wealth of extremely rich people rather than income because the wealth is structured to not generate taxable income. I think there are two considerations here: (1) fairness, (2) good economic policy. It's certainly not fair to have such a large proportion of power concentrated in such a minuscule number of people. It's hard to see how it's a good economic policy either. We want there to be capital available to be invested in further economic activities (I think we do, anyway; there are people who would debate that). But we don't want -- and certainly don't need -- so much of it in so few hands. A wealth tax is a way to drain some of that away.