How did he "evade paying taxes"? He is not worth that $3 billion or so until the IPO occurs. (You can't owe taxes on money not yet earned.) And even after the IPO, he would not owe taxes unless he sold the stock and actually received cash in exchange for the stock.
If he is not a US citizen and does not live in the US when the IPO occurs, he owes no taxes. It's not like he owes the money and refuses to pay. He just made a legal change of status so that he will not owe the taxes if he decides to sell his stock. Nothing wrong with that.
Besides, he’s helping to “starve the beast.”
We should be more concerned about the crappy laws that make people want to leave the US rather than punishing them for leaving. We don’t need Berlin Walls in the US.