The problem here isn't that capitalism lets you have productive assets that give you a return. It's that when r > g (when the rate of return of capital is greater than the growth rate of output), inequality increases dramatically. The greater the difference between r and g, the greater the rate of increase in inequality.
This is laid out super bare in his example: he bought a house. That house is in an area that surely is past its prime in terms of growing rate of GDP growth. Which means r > g. And that means his assets give him relatively good returns, which in turn compound, which has the net effect of him getting far, far ahead of everyone else who lives in that area.
This is laid out super bare in his example: he bought a house. That house is in an area that surely is past its prime in terms of growing rate of GDP growth. Which means r > g. And that means his assets give him relatively good returns, which in turn compound, which has the net effect of him getting far, far ahead of everyone else who lives in that area.