Liberal television anchors love having David Frum on their shows. He pretends to be a conservative but makes a habit of bashing them. The latest example came on Sunday when Frum took a shot at Fox News viewers. Frum told Howard Kurtz on CNN’s “Reliable Sources” that “people who watch a lot of Fox come away knowing a lot less about important world events.” In a recent New York magazine column, Frum accused the conservative media of running an “alternative knowledge system” of “pseudo-facts and pretend information.” Frum offered no specifics on CNN to back up his claim, and Kurtz,...