The US needs to increase the estate tax and the capital gains tax.

Increasing the estate tax does not necessarily mean increasing the estate tax rate, although that can be done. Primarily it should mean defeating the methods people use to avoid the estate tax.

The motive for taxing capital gains less than ordinary income is to encourage rich people to invest. That's wise, and I agree that the capital gains tax rate should be less than the tax rate on ordinary income.

Therefore, to increase the tax rate on large amounts of capital gains, we should also increase the tax rate on large amounts of ordinary income so that the latter remains higher than the former.