Writing at Forbes, George Leef steers us beyond mere technical critiques of Thomas Picketty’s methodology and suggests we need to delve more into his philosophy: 

Those responses to Piketty, accurate though they are, do little to blunt his message that the rich are already too rich and will keep getting richer unless government steps in to impose substantially higher taxes on them. Arguing against Piketty on the grounds that inequality isn’t as great as he says is futile. It’s like trying to file down the tip on your dueling opponent’s sword – the darned thing will still be lethal.

Rather than going after Piketty’s numbers, we need to go after his philosophy.