“In my 38 years this has been the worst capital destruction and the worst rating decline in history,” Robert L. Rodriguez, the chief executive of First Pacific Advisors, a mutual fund company based in Los Angeles, said to a panel of four executives from ratings firms. “All of you should be ashamed of yourself.”

The lashing elicited scattered applause. The panelists listened, their lips pursed. Some then admitted making some mistakes but said most investors in top-rated triple-A securities would get their money back.

“We all have heard a lot of criticism over the last several months, and some of that criticism is certainly justified,” said Glenn Costello, co-head of the residential mortgage-backed securities group at Fitch Ratings. But he added that a frequent criticism of ratings firms  that they are beholden to the investment banks and mortgage companies whose securities they rate  reflected “a real lack of understanding of how we as ratings agencies go about doing what we do.”

During another discussion, managers of much-maligned collateralized debt obligations  packages of bonds that are packages of other debt  criticized the media for what they said was negative coverage of the securities. Most of the speakers on that panel asked that reporters be allowed in the session only if they did not directly quote their remarks or did so with their permission.

But other managers and bankers said investors and journalists were right to question why so much wealth was destroyed so quickly. As for the view that some securities are trading at far lower prices than they deserved to be, Len Blum, a managing director at Westwood Capital, a boutique investment bank based in New York, said investors always overreacted to bad news, just as they overreacted to good news.

“The market always paints with a broad brush,” he said.

Another banker, Joseph M. Donovan, said the hand-wringing was overdone. He said what ailed the market was clear, but added that solutions would take time.

In his estimation, defaults are highest in cases where lenders take too many risks because neither they nor borrowers have much to lose. Mortgage companies sold the loans to Wall Street banks, and homeowners did not put any money down. Mr. Donovan, a retired Credit Suisse executive, said the packagers of the securities and investors took false comfort from the diversity of loans backing their securities.