Turner, in a speech Tuesday to the National Association of Television Programming Executives, also targeted "gigantic companies whose agenda goes beyond broadcasting" for timidity in challenging the Bush White House.
"There's one network, Fox, that's a propaganda voice for them," the cable news pioneer said. "It's certainly legal. But it does pose problems for our democracy when the news is 'dumbed-down.'"
Fox News in New York issued a statement saying, "Ted is understandably bitter having lost his ratings, his network and now his mind — we wish him well."
Turner, 66, stepped down as vice chairman of AOL Time Warner in May 2003.
During a question-and-answer session moderated by former CNN anchorman Bernard Shaw, Turner called it "not necessarily a bad thing" that Fox ratings top CNN and other cable news networks.
"Adolf Hitler was more popular in Germany in the early '30s than ... people that were running against him," Turner said in remarks videotaped by conference administrators. "So just because you're bigger doesn't mean you're right."
Convention spokeswoman Michelle Mikoljak said the association had no comment about Turner's comments.
Turner heads an Atlanta-based philanthropic and business empire.
By Ken Ritter