Mutual Funds Are Risky?

I thought mutual funds were good, safe investments. What the heck are ya talking about? They seem like safe investments and we are always hearing to diversify our portfolio. We turn our hard earned money over to a fund manager and hope all will go well. When the market is up they can do very well but when the market is down they lose more than any other investments. Many people will not be able to retire because they are relying on their 401k and very likely the money they thought they would have will not be there when they need it!