Right, but he's not arguing that at the far extreme level of 100% tax rates, we would see revenue decline, but a different argument that tax rate increases from current levels all the way through that extreme won't reduce deficits. It's false. We could easily raise enough taxes to eliminate our deficit. We could raise enough to spend quite a bit more than current levels.
FWIW, the Laffer curve is fine as an example that there is A level of taxes that's too high, and above which evasion and disincentives to work will reduce revenue, but for all practical purposes, in real life, it's just trotted out there for dishonest reasons to pretend that tax cuts won't reduce tax revenues. It's a lie, and asks us to believe in a free lunch.
No one knows the magic peak, or even how to measure it. Is it marginal tax rates? Effective tax rates? Top nominal rate? Whatever it is, we are WAY below that rate, and so the Laffer Curve is useless in any real world example that we've faced since the Kennedy/LBJ tax cuts in the 1960s, so for my entire lifetime.
