If you look more closely, though, the Right Answer is actually in there, but it's buried pretty deep inside the leftist rhetoric:

The reality is that for the past 40 years, Wall Street and the billionaire class has rigged the rules to redistribute wealth and income to the wealthiest and most powerful people of this country.

This is the problem.   It is not income or wealth disparity per se.  If the differences in income and wealth were entirely reflective of people's productivity and contributions to society there would be no problem.  But they aren't.  Instead what is happening is that the ultra-wealthy are using their disposable income to buy political influence, then using that influence to get laws passed that allow them to collect rents.  They then apply the proceeds of those rents to buy more political influence.  The result is a positive-feedback loop that concentrates power in the hands of a small minority and thus undermines both democracy and capitalism.