I agree with you. Rather than arguing against progressive taxes in general, I think his point would have been stronger if it had explicitly argued for taxing wealth directly, rather than looking only at income. It's narrowly true that it doesn't make sense to tax someone far more for earning nothing in years 1-9 then $1M in year 10, vs someone earning 100k per year for 10 years. (Although in reality the person earning the lump sum would probably be able to spread that tax burden over multiple years using a corporate structure, etc. But still, the basic point holds.) The logical conclusion though is to look not just at annual income but at overall net worth when determining tax owed.
Of course, there are two major obstacles to that happening. First, income taxes are very convenient, because income is much easier to measure than net worth, and one would have to be careful with net worth taxes to make sure they don't have unintended consequences around illiquid wealth. Second, a lot of powerful rich people would be against it.
Of course, there are two major obstacles to that happening. First, income taxes are very convenient, because income is much easier to measure than net worth, and one would have to be careful with net worth taxes to make sure they don't have unintended consequences around illiquid wealth. Second, a lot of powerful rich people would be against it.