On the wall in my studio, above the phones the interns work to screen callers to the program, is a list with scores of names on it. These are the callers who are not allowed to voice their opinions on the program. Many are simply lonely and bored would-be opinionators who spend their days calling every talk show they can. Some are extremists from both ends of the political spectrum. Others are obsessives who defy categorization and for whom any day is a day to expound on a single, overarching evil in the world.

A handful arrive bearing grudges against particular individuals, but most have enemies in the millions. The still-reigning world champion category of the enemies of paranoids are the Jews.

And some, sadly, are just mentally ill.

The most important lesson my interns learn has nothing to do with the machinery of production or the intricacies of guest booking, and everything to do with the incredible variety of human beings in this land.

The vast majority of Americans with deeply felt political convictions are wonderful people, even though half of them are wrong on any issue on which there is evenly divided opinion. But there is a huge difference between rotten and wrong, and all of my colleagues are eager for good-spirited representatives of the wrong to call our programs and engage in the national debate. We all have our own rules of civil discourse and the Federal Communications Commission has its own set of commands, but America is by and large an incredibly civil place where the arguments over politics and God stay far from violence or threats of violence.

Our list exists for a reason. Most of the time the media tries, correctly, to avoid providing the fundamentally disturbed among us a forum or too much attention lest they use extreme rhetoric or actions to attract even more attention. This is why fringe funeral demonstrators should be ignored and ranting callers kept off the airwaves, and why NBC's decision to air the tapes of the Virginia Tech killer in April 2007 was such a terrible one. That which gets rewarded gets repeated, and every unbalanced fanatic who watches a killer achieve even momentary fame can note the directions on the map to national infamy.

In a nation of 300 million, the far right 1 percent and the far left 1 percent each total 3 million. And if all 300-plus million of us were lined up from most violent to nonviolent, there are tens of thousands of people with guns who are quick to anger and act, though the extent of the crossover with the political extremes is unknown. The vast majority of murder in America has nothing to do with politics.

How many people are armed and intent on public violence of the sort that struck down Rep. Gabrielle Giffords, D-Ariz., and so many other innocents on Saturday? There must be thousands at least who entertain the idea every day, and though most in this category in recent years have been jihadists, there are clearly extremists from both fringes who think these dark thoughts. Many others who have no coherent political ideology have only a collection of rages as diverse as Saturday's killer's bizarre bookshelf.

The questions are: Do you want the government to go looking for these people? Should that net be big enough to catch the simply insane whose heads are filled up with many voices and demons? And what would you do with those that are found?

Saturday's media coverage of the killings lurched quickly into the hunt for the perpetrators behind the killer, as it always does, and for the same reason it always happens: We grieve for the dead and the wounded and wish for a way to stop the next Columbine, the next Oklahoma City, the next Fort Hood, the next Virginia Tech or Holocaust Museum massacre.

The sad, hard truth is that evil in the world and in each and every human being breaks out sometimes into horrific slaughter of innocents. Most of the killers are simply loners who carry the blame, not their parents or schools or video games, not talk radio or the Daily Kos or even the writers of the books on the shelves in their bedrooms.

Those who plan and commit political violence, in the name of God or a cause, are very different from the deranged, and it is crucial to keep the two categories apart. Against the former the engines of the state can and should be turned, but the defense against the latter is mostly the vigilance of those who love them for what they once were and could again be.

Those in this last group -- the families, friends, neighbors and employers of the people who have lost their way and struggle with mental illness or delusional politics and may mix that illness with a capacity for violence -- have a burden that is already immense, but it also includes the responsibility to watch the unbalanced and, when necessary, warn the community of the risk.

Examiner Columnist Hugh Hewitt is a law professor at Chapman University Law School and a nationally syndicated radio talk show host who blogs daily at HughHewitt.com.