If you’re old enough to have admired CBS in its heyday, watching its decline has been painful.Decades ago, it was dubbed the Tiffany Network – home of the great journalist Walter Cronkite (“the most trusted man in America”), and innovator of the top-flight magazine program, 60 Minutes.Even outside its news division, the network was a place where the variety-show host Ed Sullivan could break down racial exclusion by inviting outstanding Black entertainers to his Sunday night program; that was controversial in an era of intense racial turmoil. The CBS news department had some of the best journalists in the nation,...