Sometimes, against what we would hope are their better instincts, the respected machers of the cable media world make the mistake of showing the world what a painfully lame sense of humor they have. On CNN’s “The Situation Room” yesterday — in an episode we assume was meant to be funny — the channel’s senior analyst Jeff Greenfield let loose with an inane criticism of Democratic Senator Barack Obama’s wardrobe, upping the ante on the Washington Post’s Hillary/Barack silliness from last week.

The difference is that while the Post’s story was little more than a bit of political scene setting, Greenfield’s comments comparing Senator Obama to Osama bin Laden and Iranian president Mahmoud Ahmadinejad, was confounding for its sheer pointlessness and intellectual vapidity.

Greenfield began by telling us that Obama was in New Hampshire over the weekend, “sporting what’s getting to be the classic Obama look. Call it business casual, a jacket, a collared shirt, but no tie.”

How did Greenfield go from a rundown of what the senator was wearing to a comparison to two of the United States’ biggest bogeymen? The path was less complicated than you might think.

Greenfield says that the jacket-without-a-tie “is a look the senator seems to favor,” but “he may be walking around with a sartorial time bomb.”

Here’s where Greenfield goes completely off the reservation — so much so that we have no idea how this wasn’t cut before airtime. “Ask yourself,” Greenfield says, “is there any other major public figure who dresses the way [Obama] does? Why, yes. It is Iranian President Mahmoud Ahmadinejad, who, unlike most of his predecessors, seems to have skipped through enough copies of GQ to find the jacket-and-no-tie look agreeable. And maybe that’s not the comparison a possible presidential contender really wants to evoke.”

That’s right, he actually drew a connection between a U.S. senator and possible presidential candidate and the Holocaust-denying, terrorist-supporting president of Iran —because neither wears a tie. But the most amateurish — and for CNN and Greenfield, the most embarrassing — part of the broadcast was still to come.

“Now, it is one thing to have a last name that sounds like Osama and a middle name, Hussein, that is probably less than helpful,” Greenfield blundered on, “but an outfit that reminds people of a charter member of the axis of evil, why, this could leave his presidential hopes hanging by a thread. Or is that threads?”

Now, we’re not quite so prudish as to demand that every piece of news that CNN, Fox, MSNBC, etc. broadcasts must deal with weighty issues. In a 24-hour news cycle there’s going to be some filler. But when an allegedly serious person, such as Greenfield, trots out such lightweight — and nonsensical — material we have no choice but to call him on the mat.

Next stop on the Jeff Greenfield tour, ladies and germs? The Poconos. At least the amateur circuit.

Paul McLeary is senior editor of Defense Technology International magazine, and is a former CJR staffer.