But here, "justice" seems to mean the opposite. No matter how the poker game works out, the dealer redistributes the winnings to everyone including those who made foolish bets.
For what it's worth, I think that capital gains should be taxed at a lower rate because people are putting their own wealth on the line. Someone who buys a stock with $100 could lose the entire $100. Yet if that person gets a dividend of, say, $3 in return for the investment, the authors want this $3 to be treated like ordinary income. But people in regular jobs don't put any capital at risk. The worst that can happen is that the boss cheats them and they don't get paid. In other words, they don't get the $3. They don't put any of their savings at risk.