At the National Gallery of Art on Monday, visitors gathered around the blank wall with a little pockmark in it, staring and shaking their heads.

Every so often, someone would try to take a picture of the empty space but was stopped by a security guard, whose chest was maybe a bit more puffed up than usual.

“No cameras. No cameras, please,” he said, crisply.

Then he leaned over and told me: “It’s been really busy today. Everyone wants to see nothing.”

For Smithsonian groupies and guards, the Freaky Friday attack on an $80 million Paul Gauguin nudie painting was the ultimate red alert. The danger is in turning a rare episode of violence into a typical Washington security freakout.

Here are the particulars: an Alexandria woman named Susan J. Burns visited the gallery, which is free to the public, open to anyone, on her 53rd birthday, which also happened to be April Fools’ Day.

According to court documents, Burns walked through the gallery mezzanine and suddenly went after Gauguin’s “Two Tahitian Women,” pounding it with her fist and trying to pull it off the wall.

Standing about 12 feet away, a museum guard sprang into action and grabbed her, saving the iconic painting of two partially clothed women from the raging birthday girl.

After she was read her Miranda rights, Burns offered the officer her biting critique of the artist:

“I feel that Gauguin is evil. He has nudity, and it is bad for the children. He had two women in the painting, and it’s very homosexual,” she told the officer, according to court papers.

Bingo. She’d just confirmed what everyone was buzzing about Monday.

“The nudity must’ve bothered her,” said a frustrated Igal Maoz, a New York artist who’d travelled to D.C. just for the Gauguin exhibit and was crestfallen when he learned that the painting had been removed for inspection after the attack.

“There are other paintings with even more nudity!” another visitor pointed out to me, and we walked over to another work, “Te Pape Nave” (“Delectable Waters”) and counted five bare breasts, not just the three that allegedly so unnerved Burns.

It’s not the first time someone has come undone over the sight of human mammaries — metal, oil or flesh — in the nation’s capital. Former attorney general John Ashcroft famously ordered drapes to shield the bare chest of an aluminum Lady Justice statue in the Department of Justice.

More recently, the guards at the Hirshhorn Museum were flustered by a woman who was breast-feeding her infant on an indoor bench.

Throughout any art museum, it’s difficult to avoid the naked human form.

Heck, you don’t even have to go inside the gallery to confront more full-frontal nudity than HBO offers. Few school groups have walked past the Court of Neptune Fountain outside the Library of Congress without noticing the lusty, bronze features of the cavorting bunch.

No, even if we do wig out over the occasional risque work, Washington wouldn’t be able to follow Burns’s ethos and completely do away with public displays of nudity.

(Of course, The Washington Post’s Web site offered increasingly modest photos of the painting as the story progressed over the day.)

Still, there’s no way our angst about nakedness rivals our fears over security. How long will it be before someone suggests placing bollards around every one of the National Gallery’s thousands of works of art? Perhaps glass cases or walls would keep these treasures safe. Or maybe an alarm system surrounding every painting?

After all, this is one of the few places in the world where anyone can walk in, free of charge, and stand inches away from cultural treasures. Aside from a simple purse search, getting access to priceless stuff in Washington is easier than weaving through cherry blossom traffic jams.

“We really don’t believe in placing barriers between the art and people,” said gallery spokeswoman Deborah Ziska. “Our guards do an amazing job.”

Indeed, they do. I’ve never once visited the gallery without a guard’s tractor beam locking in on my small children, watching their every move. They can mind-read a toddler’s idea to climb a sculpture long before he’s trundled close to any tempting Calder.

No, there is no need for more metal detectors or wand searches or scanners to keep our national treasures safe.

Just listen to what Burns allegedly told the guard once she was cuffed, and you’ll know there was no way to stop her attack:

“I am from the American CIA, and I have a radio in my head. I am going to kill you.”

Security barriers aren’t always the answer to protect us from danger. Sometimes, a little bit of help for a troubled soul will do the trick.