By Steve Chapman - November 7, 2013

For travelers, the modern airport has become an obstacle course of security precautions, where everything not prohibited is mandatory. Boarding a plane is an exercise in indignity that strips passengers of jackets, shoes and belts before subjecting them to machines that see through their clothes and security agents who touch their junk.

In spite of all this, airports are not immune from lunatics with bad intentions. Last week, a man with a rifle shot three Transportation Security Administration agents at Los Angeles International Airport, killing one.

This episode evoked the same response as every other aviation attack: the impulse to devise a quick solution. The union representing TSA employees urged that at least some security screeners be armed -- a request administrator John Pistole promised to consider. As it stands, said David Borer, general counsel of the American Federation of Government Employees, "they're sitting ducks like everyone else."

That's true. But it's not true that equipping them with guns would alter their plight. Complete safety, for agents or passengers, is an impossible dream.

Even armed agents can't necessarily foil a determined gunman who is willing to die. And imagine the chaos of a screener trying to shoot an attacker (or worse, a group of them) amid a mob of travelers. The result could be more bloodshed, not less.

Giving screeners guns would be no help against someone with a bomb, who could detonate a device before anyone knew what was happening. Nor would they prevent terrorists and maniacs from carrying out attacks at ticket counters, baggage carousels or taxi stands. Aspiring killers adapt to new preventive steps, and this one would not be hard to outwit.

Maybe the change would divert an assailant from screeners to civilians. But that would be an odd achievement. Aren't the screeners there to protect travelers, not the other way around?

"Wherever you establish a security perimeter, by definition, there's stuff outside it," MIT aviation security expert Arnold Barnett told The New York Times. You just can't expand it far enough to include everything. The calls to expand the existing one bring to mind Abraham Lincoln's story about the farmer who said, "I ain't greedy about land; I only just wants what jines mine."

The security-above-all mindset, however, is not easy to overcome. After years of relieving travelers of tiny pocketknives, the TSA decided its employees should allow them in order to focus on more formidable dangers, like explosives. But outcries from flight attendants unions and members of Congress forced the agency to retreat.

Never mind that terrorists can board a flight with scissors, knitting needles and 6-inch screwdrivers, which could be rendered more lethal than a penknife. Never mind that stabbings of flight attendants were not a major problem before 9/11 precipitated the ban. The driving assumption is that you can never be too careful.

But you can, of course. Training TSA agents to carry firearms would cost money. Deploying more police in airports, another option, would cost more as well, since cops get paid more than screeners. Concentrating cops at checkpoints would invite terrorists to locate their massacres elsewhere in the terminal.

Not to mention that given the rarity of attacks like the one at LAX -- the first time in the TSA's 12-year history that an agent was killed on duty -- none of these steps may save a single life. They make about as much sense as putting the National Guard in movie theaters in the wake of the Aurora, Colo., massacre.

Actually, they make less sense, in light of the risks of introducing thousands of guns into small, crowded spaces filled with people who really hate being there. The change is more likely to lead to an agent shooting someone than to prevent someone from shooting an agent.

Equipping screeners with deadly weapons would also heighten the sense of coercion and intrusion that makes air travel resemble admission to a medium-security prison. Being ordered around and physically groped by a uniformed officer is bad, but it would be worse if he had a Glock on his hip.

The suspect in the LAX attack apparently had some grudge that drove him to target airport agents. If anti-TSA fury can motivate murder, it is not the height of wisdom to make the screeners more intimidating.

The obvious lesson of our post-9/11 experience is that whenever we target one danger, others emerge. But it's a lesson that can always be repeated.