Jim's called it right. The anti-egalitarian attack on Brad De Long is just silly. There are two further points they are missing:
1. Justice is not a matter of preferences. Imagine a ruthless dictatorship which had brainwashed its subjects. No-one would then envy the Great Leader his wealth and power. But we would all agree that this society was unjust. Absence of envy, then, is no evidence of justice. Nor is envy evidence of injustice. I envy Martin Simpson's talent for playing the guitar. But there's no injustice at all here.
2. What troubles many of us egalitarians is the origin of inequalities, not merely their existence. And this is where Jane Galt's analogy with beauty collapses. No-one worries about inequalities of beauty (though in the UK we do offer free plastic surgery to the extremely ugly) because they arose from a fair process - nature. And nature rarely deals anyone a full house. Sure, Tim might be shorter and less pulchritudinous than me. But he more than compensates for it in extra charm. No problem.
However, we can't be sure that inequalities of wealth are so just. Some of them have arisen from historic thefts, rent-seeking, exploitation of monopolies, capturing the state and suchlike. When Greg Mankiw says:
I see [the rich] as some combination of more talented, hard-working, and lucky than average
I just marvel at how so intelligent a man can be so naive.