Fox News has a bad habit of pretending that while its opinion shows have a point of view, its news programs are purely objective. The network routinely makes a mockery of that purported distinction, and tonight was no exception.

Martha MacCallum, a co-host of Fox's America's Newsroom, filled in for Greta Van Susteren during On the Record. The problem with this is that On the Record, which airs weeknights at 10 p.m., is billed by Fox as an opinion program, while America's Newsroom, which airs weekdays from 9 to 11 a.m., is part of Fox's “straight news” division. Indeed, in 2009 The New York Times reported, “Fox argues that its news hours -- 9 a.m. to 4 p.m. and 6 to 8 p.m. on weekdays -- are objective,” and quoted Michael Clemente, the channel's senior vice president for news, as saying: “The average consumer certainly knows the difference between the A section of the newspaper and the editorial page.”

Clearly Fox doesn't find anything wrong with treating its opinion and “straight news” hosts as interchangeable. And while MacCallum has in the past filled in as a co-host on Fox & Friends, another of Fox's opinion programs, anchoring a primetime opinion show is a significant step beyond that. This isn't surprising, of course, but it is further evidence that there is no distinction between Fox's “straight news” and opinion divisions.