> Otherwise where does the wealth used to pay the taxes come from?

Consumers.

> Capital only generates a return in a context where there is someone to consume what it produces.

Exactly. If you don't tax the return sufficiently it amplifies the capital (lands in th pockets of billionaires in other words).

> It seems like a counter-intuitive position to take if you've identified that billionaire wealth is a key justification and the billionaires are very good at extracting money from the government. It seems likely to me that billionaire wealth would scale with the size of government.

What billionaires extract from the government in terms of subsidies and such is nothing compared to what they get as a result of tax cuts and being undertaxed in general.

Basically we should tax billionaires more. Government getting richer because of that is just a side effect.

Government growing with the size of the economy is not a goal. It's a gauge showing us that billionaires are adequately taxed.

I'm using term "billionaires" loosely. 10 hecto-millionaires are fine too as a replacement for one billionaire.

Again the goal is not to fund the government. It's to remove power from unelected oligarchs.