I'm not by any stretch of the imagination against people making money, but you have an obligation to pay it forward to the society that enabled you to do it. Defending this sort of behavior smacks of the wealth-worshipper disease and there's not a lot worse than that.
What would be satisfactory? That he paid based on the ipo price? What the stock is worth at the end of ipo day (likely inflated)? What it's worth a year from now? 5 years? 10 years? What would be fair?
If I understand the situation correctly. He is basically going to be allowed to pay capital gains on $X after selling for something like $10X, making his rate more like 1.5%.
If you want to continue the discussion, do you think you could try to do without the personal attacks? They're very irritating and completely uncalled for here.
Saverin's paying 15%. Sounds like the goal is met.