This is a difficult issue. How can the government prevent holders of very liquid assets from dumping those assets during a market panic - other than by providing a governmental backstop? And if the government does provide a backstop, there is really no difference between a money market fund investing in private assets and a government securities fund, in that investors in both funds can look to the government as the ultimate obligor.
This is an issue that the incoming majority at the SEC will have to address. The solution is not at all obvious, if in fact one exists. How is it possible for there to be an instrument that promises immediate liquidity yet limits that liquidity when investors most demand it?