Is income disparity essential for growth?

Elon Musk has been moaning that he pays too much tax. He wants to keep more of the $14 billion or so that he earns each year. But has he got a point? Do we need to the opportunity to become incredibly wealthy to drive innovation. If we had more equal levels of income, would we actually suffer from lower growth, so everyone would end up worse off.? Phi puts the question to Steve Keen on this Christmas edition of the Debunking Economics podcast.