There is an interview of Piketty in le Monde today, and what he says seems to confirm my suspicion.

Loosely translated, answering a question about the fact that we don't hear too many stringent criticisms of his book (whereas several have praised it), even though there must be many opponents of his theories, with easy access to the media:

"We don't hear them much because my book is not a book of theory or speculation. By the end, I draw conclusions with which one may disagree, but the large majority of the book is made of descriptions of the historical of inequalities of assets holdings. I think it is not something easily brushed away. [...] people may draw different conclusions, but the diagnosis is hard to dispute."

By the way, it's interesting that potential critics are understood to necessarily come from the right. However, much as I appreciate his tremendous historical work, I feel that if anything he errs towards the right. In the description, as he himself says, because official data would tend to understate the extent of inequalities (tax havens have become a bigger factor with the increased mobility of capital). And in highlighting policy causes, probably deliberately so that his work cannot be brushed aside.

Which makes Galbraith remark (clearly intended as a negative) that this, despite wanting to be, is not the definitive work on Capital fall flat. First, being a definitive work is a silly target (why would you not want people to add?). But second, because Piketty deliberately made sure it would not be. He wanted it to be readable by all and dismissable by none.

This book (and the World Top Income Database. In many ways, the book is a summary of the base and an example of what can be done with it) is so important because it forces open a whole area of investigation. It does not seek to close anything.

Earth provides enough to satisfy every man's need, but not every man's greed. Gandhi