[Don Corleone]

He didn’t say it was a good theory, or a legitimate theory or that the theory had any credence to it.”

Then why did he say it at all??? Hmmmmm? Could it be because he has nothing else to say?

[Paul Atreides]

It gets the idea out there, without actually making the charge. It's the equivalent of beauty parlor gossip: "Why, I've actually heard some people speculate that Madge is cheating on her husband, but I've not heard it from anyone reliable."