The stock market and the companies in it are all subject to the pressures of the free market system. Judge Posner seems to believe that mutual fund managers aren't. How can that be? The market may not be perfect, but it is certainly more efficient than any regulator will be in setting prices for fund managers. Based on my own experience with insurance regulators, one thing was perfectly clear, the more regulators got involved the higher prices were.
If, as one person commented, mutual fund investors are "infants" and do not have the time or willingness to do their research, those investors have no business buying and selling any stocks or mutual funds. They need to turn their money over to a professional.
As for the other comment that the investor may be subject to taxes on the sale to get out of a high priced mutual fund. if the investor had done any research originally, this situation probably would not have happened.