After having spent somewhere between three and nine years lamenting the (excessive, to my mind) levels of concern the American populace seems to have about terrorism, I've come to an uncomfortable realization: terrorism is oddly comforting to panic about.
Think about it. Terrorists are usually members of an outside group who are motivated by factors that are easily summarized into nice, neat packages of rationale. You may never actually understand their reasons, but that's kind of the point: as long as you can't understand them, they remain safely the Other. Facing threats from outside forces tends to cause disparate members of a group to band more tightly together, feeling the security in numbers and like attitude concerning at least this one situation.
For some reason, after an attempted or successful terrorist attack, those who generally espouse a limited, hands-off government suddenly start lamenting the failure of the government to know everything that everyone is doing. His dad was worried, but he still had a visa and didn't check luggage and paid in cash—how dare the system not have picked him out of the millions of people flying that day and immediately halted everything to protect us? (This is not to say our cross-checking and red-flagging system couldn't use some work; it seems obvious it was not actually designed as a coherent unit.)
These same people, however, are the ones who decry any attempt at gun control, protective vehicle legislation, or anything that gives the government more knowledge of their whereabouts or behavior. How ironic. What would be the most terror-inducing thing of all? A genuine realization of how little keeps those surrounding us from killing us all.
Think about it. What is actually keeping your coworker, roommate, teacher, doctor, food producer, or random person on the subway/road/sidewalk from killing you or your loved ones? Not a whole lot. I'm sure a considerable portion of the populace has at one point or another had the realization while hurtling down a highway that the only thing keeping them from sudden death or dismemberment is an absurdly insubstantial line of paint on the pavement. You get a queasy feeling, perhaps from the sudden related realization that you could actually kill yourself and others just with a sudden flick of your wrists, and there's absolutely nothing keeping you from doing this...not that you want to or plan to, but if you did, what would stop you? And if nothing's stopping you but your general presumably healthy state of mind and attachment to life and your fellow beings, what's stopping the guy in the next lane?
It's kind of amazing how much faith we're putting in social norms. I suppose some would argue it would take a severe mental illness to cause someone to swerve into another car or pedestrians for absolutely no reason or to jump in front of a train, possibly derailing it and definitely traumatizing everyone around, to deliberately infect our food supply with a contaminant, or certainly to take a gun and open fire on whoever's nearby. I'm not really sure that's the case, though. Especially in the car case, I'm pretty sure it doesn't take a substantial mental illness, just a sudden awareness of how absurd it actually is to drive a two-ton hunk of metal at 60+ miles an hour mere feet from dozens of others doing the same and then a slight twist in whatever brain chemicals are involved in impulse control. Thinking "If I just turned the wheel suddenly, I would go hurtling over there into those cars and we would all die" isn't really all that far removed from doing it, I don't think. Thinking about specific muscle movements like that primes the muscles to do the action being considered, even if it's only being considered in the abstract.
Even with shooting rampages, I think we'd be surprised how little the changes in mental states that are required to do something like that actually are. I'm sure we've all been in blind rages before, our natural senses of what's fair and right and proper temporarily suspended as we indulge in pure anger or hate. If you have a gun in your car when you get unfairly fired, you're much more likely to go back into your office and shoot your jerk of a boss than if you don't, obviously. (I have no real stats to back this up, but I did read something a while back that did have statistics supporting a similar case that those considering suicide actually followed through at much higher rates when they had a gun or a supply of sedatives or a bridge they had to cross on their way home than those who would have had to go out and buy a gun or get a prescription or go seek out a bridge. The combination of a fairly common state of mind that would turn out to be no biggie if the means weren't there with the means actually being there causes people to do things they wouldn't do if they required slightly more thought or effort.)
Anyway, my point is that mental illness or no—and it doesn't really matter, as there are plenty of people running around with mental illnesses, too, and as far as I'm aware, the government doesn't keep terribly close tabs on them either—you probably encounter scores of people every day who have the means to kill you; you're just banking on their not being in the mood to. And what does the government do to keep you safe from your neighbors? Not a whole lot in the grand scheme of things. Yes, we keep felons from (legally) purchasing guns, convicted sex offenders from living too close to potential victims, and those whose mental illnesses make them demonstrably a threat to society from roaming free, but the vast majority of these protections share exactly the problem of the government's approach to terrorism: they're all retroactive. Only after someone uses liquids to try to blow up a plane are liquids banned from carry-ons; only after someone kills someone do we keep them from buying another gun.
Obviously there's no way for the government to actually be big enough, strong enough, and involved enough to actually protect us from a twitch in someone's brain chemistry suddenly causing them to swerve into another car—nor do even the biggest proponents of big government desire such a thing. So why do we expect the government to protect us from religious extremists who want to blow up planes with their shoes but not from teachers who have finally had it up to here potentially killing their idiotic students or the like?
Really, the events of the past few years are slowly making me realize is that it's really quite difficult to figure out in advance what sort of people might be dangerous. The Virginia Tech shooting, the Fort Hood shooting, the underwear bomber—yes, there were "warning signs" visible to anyone paying attention, but really, how happy would we be if the authorities took every single warning sign of the same significance seriously? Does anyone really want to suddenly be an object of scrutiny any time he or she says, "Gah, I'm so mad at X I could kill him/her" or "Ugh, I wish people who believe/do Y would suddenly drop dead"? We've all said it. There are loads of mentally unhealthy people who are romantically spurned, and the vast majority of them don't shoot up classrooms of students—how do you discriminate between the ones who are likely to do so and those who are likely to sit around and write crappy poems and mope about for a year or two, or who might commit suicide but are no danger to others? As far as I'm aware, we don't understand mental processes well enough to do so. If anyone you know committed suicide tomorrow, you would probably suddenly remember something they said or did or that had happened to them in the past month or so that clearly indicated how depressed they were. Does the fact that the other however-many people you know have said or done similar things recently necessarily mean they're going to kill themselves? Obviously not. Let's not forget that the lines between mental health and mental illness are pretty blurry (until something happens), as are the lines between an abnormal but harmless passion for a cause and overzealous devotion to it. There is probably a series of situations that could turn anyone into a killer, so let's not all feel so distinct from and superior to the sorts of people who do.
I suppose my original point was that it's much more comfortable to panic over extremist Muslim terrorists (Them) who are attacking Us due to a difficult-to-grok-yet-easily-stated reason than it is to think about all the other shades of danger we face from those we think are pretty much like us. It's much more difficult to understand why some disaffected teenage guy would go on a shooting rampage (without suddenly declaring that he must have been mentally ill, thus shoving him nicely back into the camp of Other) than why people from some group that's pretty foreign to us would hate us and want to wipe us out. Us vs. Them, good vs. evil, our god vs. theirs, our worldview vs. theirs—these are all easily understood and surprisingly comforting ways to think about a threat or struggle. Us vs. Us, human nature vs. human nature, very similar worldviews vs. each other—not so much.
I very strongly recommend reading The Banality of Evil to everyone. (This post was not inspired by that, but it's quite relevant.)