Owning that much of a company that is valued that highly is still damaging to society, even if it isn't liquid cash. Even putting aside their ability to take out loans with the shares as collateral, if the company is really worth that much it should be owned by a larger number of people with each taking a reasonably sized share to ensure that decisions are not made selfishly.
Taxing unrealised gains also hurt working class people dabbling in the stock market to try and improve their circumstance. IMO once you reach a net worth of $1B you get a pat on the back that you won captalism, and a 200% tax rate on anything beyond that to force you to give it up. No one person should own and control so much of a company if it truely has so much value, divide it among those that created the value i.e. the employees.
This 100%, too many musk fanboys don't understand how much he is actually hindering innovation.
Even at SpaceX they make more progress when he isn't involved.