"Somebody, sometime has got to take a stand and say democracy cannot survive, much less thrive with the level of big corporate and big government interference and intimidation in news," he said on CNN's "Larry King Live."
In the suit, filed a day earlier in state Supreme Court in Manhattan, Rather claimed CBS and Viacom Inc. used him as a "scapegoat" and intentionally botched the aftermath of a discredited story about President George W. Bush's military service to curry favor with the White House. He was removed from his "CBS Evening News" post in March 2005.
"They sacrificed support for independent journalism for corporate financial gain, and in so doing, I think they undermined a lot at CBS News," he told King.
Rather did not mention other instances in which he believed news organizations bowed to corporate and government pressure.
CBS spokesman Dana McClintock did not return an after-hours call seeking comment Thursday. He has called Rather's complaints "old news" and said the lawsuit was "without merit." A spokesman for Viacom declined to comment.
Journalism ethics scholar Bob Steele said Rather would have a difficult time proving that the White House or other political operatives exerted undue influence on CBS.
"It would be naive for us to believe that there was no influence from powerful institutions and individuals on journalism," said Steele, a scholar at the Poynter Institute, a journalism foundation in St. Petersburg, Florida.
Still, he said: "For the most part, the journalists who run news organizations and who report the news fight hard to protect the independence of the journalism, and most of the time succeed."
Rather narrated the September 2004 report that said Mr. Bush disobeyed orders and shirked some of his duties during his National Guard service. It also said a commander felt pressured to sugarcoat Mr. Bush's record.
The story relied on four documents, supposedly written by Mr. Bush's commander in the Texas Air National Guard, the late Lt. Col. Jerry Killian. Critics questioned the documents' authenticity and suggested they were forged.
A panel selected by the network to investigate the story determined that it was neither fair nor accurate. CBS fired the story's producer and asked for the resignations of three executives because it could not authenticate documents used in the story. Rather was forced out of the anchor chair he had occupied for 24 years.
On CNN, Rather dismissed the panel's review, claiming it was not impartial.
"This was in many ways a fraud. It was a setup," he told King.
Louis D. Boccardi, the retired chief executive of The Associated Press who made up the two-man investigative panel with Richard Thornburgh, the former U.S. attorney general, defended the panel's work Thursday night.
"Our report was independent, and it speaks for itself," he said, echoing comments made by Thornburgh on Wednesday. Both declined to comment further.