The desirability of income equality is a fatally flawed idea. Let's remember the important principle, "From each according to his ability and to each according to his needs." That does not advocate equality.
Within limits income inequality is not a big problem. Inequality becomes a big problem if some individual incomes fall below a subsistence level, or if aggregate investor income exceeds the total investment expenditure.
As Piketty reminds us, R > G is an important cause of our economic problems and is due to no upper limits on wealth. R > G is best understood when seen as theory. Data supports R > G, but that data is buried in a sea of other factors, and that makes it easy to discount the importance of R > G.
When aggregate investor income exceeds the total investment expenditure that income surplus leads to speculation bubbles and the need to tax or borrow that surplus income to allow money to circulate. It's not the inequality itself that matters so much; it's the various troubles caused trying to get that money back into circulation. R > G is easy to understand without any need for a big book of fuzzy data. Must we know the temperature before using a fire hose?
Must the left ignore all opposition to equality? Why reject Marx along with other logical opposition to income equality? There are various good reasons and logical justifications for some income inequality, but they don't excuse allowing anyone's income to fall to zero. It doesn't matter to starving people how much more income others are getting. It's not the inequality that matters. It's the hunger and homelessness that count.
Ending our dependence on wages and thus our need for suicidal growth does not require equality. It does require placing hard limits on the extreme venality of a few sociopaths. Muddled thinking is invited by acceptance of the impossible goal of income equality. Support the wise and visionary goals of giving for needs and taking from abilities.
Barry http://home.earthlink.net/~durable/