Billionaires should pay a wealth tax is considered a far left position.
Billionaires should pay an income tax is a position supported by all except maybe some tea party folk.
The problem is that stocks aren't income. Stocks don't have a value until you sell them. How do you tax that? One day someone can be worth billions and the next nothing if the stocks they own drop in value or the company goes bankrupt. I don't know the solution but it's not as easy as most people make it out to be.