Thomas Piketty — French Economist born on May 07, 1971,

Thomas Piketty is a French economist who works on wealth and income inequality. He is a professor at the École des hautes études en sciences sociales, professor at the Paris School of Economics and Centennial professor at the London School of Economics new International Inequalities Institute... (wikipedia)

You need some inequality to grow... but extreme inequality is not only useless but can be harmful to growth because it reduces mobility and can lead to political capture of our democratic institutions.
Economists tend to think they are much, much smarter than historians, than everybody. And this is a bit too much because at the end of the day, we don't know very much in economics.
I think inequality is fine, as long as it is in the common interest. The problem is when it gets so extreme, when it becomes excessive.
My premise is not to tax to destroy the wealth of the wealthy; it's to increase the wealth of the bottom and the middle class.
We want capitalism and market forces to be the slave of democracy rather than the opposite.