Your last paragraph is the key being able to justify high tax rates. "Wealth" or "net worth" taxing is punitive. I'm sure you're aware, but if anyone else reads this here's why.
Let's say you start a company called HealthBook (HB). HB uses technology and social networking to identify areas in healthcare where people are spending too much due to supply chain corruption which limits options for effective treatment while driving up costs ($25 aspirin). HB then works with willing facilities and, for a very small fee, greatly reduces the corruption.
HB ends up with a market value of $500 billion dollars due to its popularity and effectiveness around the world, but a sizeable percentage of it's profits are used for philanthropic purposes. Due to it's valuation, and your 60% stake in the company you're a paper billionaire.
You draw a relatively salary of $150k a year, but you're "wealth tax" is 6% of the value of your shares. You don't enough money to pay that tax so you sell shares every year to cover the expenses. In a few years time you lose control of your company because you're no longer the majority shareholder, and the very companies ripping people off have been buying up all the shares you sell, and they take control of the company and use it to once again corrupt the market.
The only proper tax is on positive value changes. Tax income over $10 million at 90%, that's fine. But taxes of "net worth" are dangerous and unfair.