Rush might have been providing an example of the logical argument that "Correlation does not imply causation."
People often make the mistake of believing that a statistical relationship necessarily implies that two events occurring together have a cause and effect relationship.
Doctommft has the example: All men who died of cancer ate carrots sometime during their lifetime. It would be a lapse of logic to believe that eating carrots causes death by cancer.
Rush can be more profound than given credit for by those on the other side of the political fence from him. I don't think he was talking about health, but about syllogisms, a form of deductive reasoning.
(Remember folks, this is not a political discussion.)