I guess it would have been simpler if he had just called them leeches.
He did an acceptable job of copying the textbook definitions of commensalism, etc. but not in defining it in terms of which benefits more, which is the heart of the matter. It was a total red herring, going after the definitions instead of explaining why he thinks that rich people don't need serfs, when in fact, the serfs could probably survive without Wall Street better than Wall Street could exist without worker bees. That is parasitism, with the host being the workers and the bankers being parasites. The bankers sucked the blood out of the economy, but didn't end up suffering... the middle class host fed them again.
The rich use their capital to extract a greater portion of the output of the workers. If the rich weren't in a position to be socking away the fruits of the labors of the workers, the workers would have it and would have even less need for risk capital and the money they pay to them them via interest.
The privatization of profits, while socializing risk and loss is clearly not a winner for the middle class but is the way the rich have altered the system. Examples are the bank bailout and oil exploration tax credits. So calling it parasitic is not really out of line.
