Maybe somebody should offer Iron Mike Tyson a TV news-talk show, although it probably won’t be MSNBC. Last week the former heavyweight champ was one of the vanishing few willing to await the evidence before pronouncing a verdict in the Trayvon Martin tragedy.

Appearing on Piers Morgan’s CNN program to promote a documentary film about his boxing career, Tyson was asked his opinion of a just-concluded interview with gunman George Zimmerman’s older brother.

“I don’t know,” Tyson said. “I wasn’t there. I don’t know what happened. I have a good opinion what happened, like everyone else … He [Robert Zimmerman] doesn’t look like a seasoned enough liar to talk to you.”

Clearly, the champ learned plenty during his time in the penitentiary — where there are many seasoned liars, almost everybody’s innocent, and some small percentage of inmates actually are. Tyson adverted to the nation’s long history of young black men falling victim to racist violence, then made himself particularly clear: “I want to believe that Mr. Zimmerman did something wrong and illegal, but I wasn’t there.”

Neither were you, dear reader; nor was I. Like Tyson, we’ve learned everything we know about this terrible event from a ratings-driven and increasingly unreliable news media. That is, we’ve been presented a melodrama in place of a news story, with speculation and downright fictionalization being presented far in advance of facts.

And sometimes, alas, in their place. But hold that thought.

In consequence, roughly half the country has gone all Nancy Grace, the blonde former prosecutor who has never seen an innocent defendant. A smaller but impassioned cohort is replaying the Greatest Hits of the late Johnny Cochrane, the flamboyant defense attorney who helped get O.J. Simpson acquitted. There’s no shortage of commentators urging a racial dialogue, when what they appear to have in mind is a lecture.

Public fallout from CNN’s interview of Robert Zimmerman basically told the story. Under polite but skeptical questioning by Piers Morgan, Zimmerman advanced his brother’s version of the confrontation between him and the 17-year-old victim. He described a scenario in which Trayvon Martin was the aggressor.

Supposedly, after a brief unfriendly exchange, Martin had broken Zimmerman’s nose with an unprovoked punch, pounded his head against the sidewalk, and then threatened to kill the self-appointed neighborhood watch volunteer with his own holstered handgun.

“George was out of breath, he was barely conscious,” Zimmerman said. “His last thing he remembers doing was moving his head from the concrete to the grass, so that if he was banged one more time he wouldn’t be, you know, wearing diapers for the rest of his life … and there would have been George dead had he not acted decisively and instantaneously.”

Morgan pressed Zimmerman to explain surveillance videos that appeared to show his brother brought into Sanford, FL police headquarters less than an hour after shooting Trayvon Martin “with no apparent markings to his face.”

“There’s no visible sign of any attack,” Morgan said. “How do you explain that?”

“We’re confident the medical records are going to explain all of George’s medical history,” Zimmerman said “because [of] how he was treated at the scene and how he was not.”

Should it come to a criminal trial, whatever those records say will definitely be important.

Nevertheless, a sometime MSNBC contributor called Toure — he goes by one name, like Madonna — confronted Morgan on his own program the next night. Over at NBC, he informed the affable Brit, people were laughing at him. He expressed righteous anger at Morgan for “allowing Robert Zimmerman to come on your show and spread misinformation and perhaps prevarication throughout the waves, which we know many people will believe.”

Toure never produced the Magic Decoder Ring enabling him to determine the truth with such certainty — except to cite the same murky police surveillance video Morgan too had referenced, and which MSNBC sleuths have broadcast as often as the Zapruder film of JFK’s assassination.

Anyway, Piers Morgan gave as good as he got; Toure later apologized.

That’s not the point.

The point is that what MSNBC called a “newly released surveillance video” showing “new angles, never seen before” exists of George Zimmerman’s entry into police headquarters that terrible night. It was broadcast once, on Martin Bashir’s daily program at 2 p.m. Central on March 29, and was alluded to momentarily on “Hardball” that evening.

And what that video clearly shows is a large goose egg and a bloody abrasion on the crown of Zimmerman’s head. Check it out for yourself. Here’s the URL, sent to me by my indefatigable friend Bob Somerby of the dailyhowler.com: http://video.msnbc.msn.com/martin-bashir/46896424/#46896424.

The implications are obvious, if anything but dispositive. That’s why it’s so alarming that the telltale video appears to have vanished into a Memory Hole while MSNBC’s ace team of talk show prosecutors pretend it never existed. Nor have rival networks broadcast it.

One Fox News network is enough.