I'd say that his critics are annoyed that he's ignoring their motte [ETA: Well, not ignoring, but not treating as the bailey], from which they're basing their assault on Income Inequality. "Come over here and fight, you coward!"

There's not much concession in agreeing that fraud is bad. Look: Fraud is bad. And income inequality is not. Income inequality that promotes or is caused by fraud is bad, but it's bad because fraud is bad, not because income inequality is bad.

It's possible to be ignorant of the portion of the intellectual landscape that includes that motte; to be unaware of fraud. It's possible to be ignorant of the portion of the intellectual landscape that doesn't include the bailey; to be unaware of wealth inequality that isn't hopelessly entangled in fraud. But once you realize that the landscape includes both, you have two conversations you can have: One about income inequality, and one about fraud.

Which is to say, you can address the motte, or you can address the bailey. You don't get to continue to pretend they're the same thing in full intellectual honesty.