Except for it has never been true. As we may have seen in the United Kingdom over the last 100 years, periods of declining inequality have been associated with wars, economic depressions, low competitiveness, and even an IMF assistance in 1976. The highest point of EQUALITY occured during the Winter of Discontent in 1978/79. No great time for Britain.
Inequality started to grow during Margaret Thatcher. It has increased until the crisis of 2008.
Conclusion? Inequality is good. When it falls, it means something really bad. At least in Britain from 1913 to date.
The main question is not to which extent Piketty manipulated the data. The fundamental question is: What is the optimum level of inequality? The first approximation of the answer is that it is not zero.