Not surprisingly, the article doesn't say what you claims it says, mcmurtry. It says a lot of things about the topic and offers several different conclusions, but not really the one you are offering. Once you get past the headline, it mostly says that celebrity endorsements don't provide the help you think they might (except for Oprah...who was a big help for Obama) and that there usually isn't a transitive property in celebrity endorsements...except when there is.
It seems to me that conservatives don't like celebrities speaking about politics...except when they speak favorably about something conservatives like. Then they are totally giddy about celebrities talking politics. See Kanye, Ted Nugent, Kid Rock, Clint Eastwood, and so-on. Towards that, I think your article mostly hits the mark. Celebrity endorsements generally don't matter much. It's just not the point you were making.