James Kwak explains it nicely:
Let’s not mince words. Kohn was one of the leading cheerleaders for the Greenspan Doctrine. Here’s one example. In 2005, Raghuram Rajan gave a now-famous paper at the Fed’s Jackson Hole conference warning of the impending financial crisis. Kohn gave a response, which we describe this way in 13 Bankers:
“Fed vice chair Donald Kohn responded by restating what he called the ‘Greenspan doctrine.’ Kohn argued that self-regulation is preferable to government regulation (“the actions of private parties to protect themselves . . . are generally quite effective. Government regulation risks undermining private regulation and financial stability”); financial innovation reduces risk (“As a consequence of greater diversification of risks and of sources of funds, problems in the financial sector are less likely to intensify shocks hitting the economy and financial market”); and Greenspan’s monetary policy resulted in a safer world (“To the extent that these policy strategies reduce the amplitude of fluctuations in output and prices and contain financial crises, risks are genuinely lower”). Kohn’s conclusion reflected the prevailing view of Greenspan at the time: “such policies [recommended by Rajan] would result in less accurate asset pricing, reduce public welfare on balance, and definitely be at odds with the tradition of policy excellence of the person whose era we are examining at this conference.”
Kohn (and Greenspan) have been proven completely wrong. The quotations in bold are utter nonsense.