The hair really has not helped. In the dock in a Colorado courtroom, his unsightly red-orange dye job setting off his bulging gray eyes, James Holmes looks likes a monster, exactly as the press has described him. "RED DEVIL," screams the New York Post, which has put him on the front page three times this week. Contrast the bible-salesman look of his high school yearbook photo with his freakish appearance at his arraignment, and you can see him recede from a full person into something other.

The dehumanization of James Holmes is now well underway. Far faster than the killers at Columbine or Virginia Tech, the alleged murderer of 12 moviegoers in Aurora, Colorado, has been turned into a nationwide symbol of irredeemable evil.

In fact, the portrayal of Holmes in the American media has less in common with those of earlier mass killers than with Jerry Sandusky, the Penn State coach now convicted of serial child molestation. The murders at Columbine did at least have the salutary effect of sparking a nationwide discussion on how young people become violent, and how we can prevent it. Not this time. Holmes, like Sandusky, is a born monster, and he must be exterminated.

It's not that I don't understand the horror and disgust. The crime of which Holmes is accused is indescribably heinous. But this week we have seen how horror leads to bloodlust – note the hundredfold spike in web traffic to learn about Colorado's capital punishment laws – and bloodlust leads to something else. When we say that Holmes and Sandusky "don't deserve to live," a refrain seen across the Internet and on talk radio, we are saying that they are something less than people. And if we convince ourselves that they are totally other, we'll never prevent future Holmeses from wreaking further chaos.

Americans, sadly, have a tendency to dismiss attempts at understanding people like Holmes as a bleeding-heart exercise in criminal sympathy. Columbine was the exception. Usually, we refuse to reckon with the complex causes of violence, let alone its future prevention, and instantly inscribe these crimes into a framework of inexplicable evil. Think of Timothy McVeigh, who spent years being radicalized in anti-government circles – and yet, after the 1995 Oklahoma City bombing, was considered only an "all-American monster".

There was Ted Kaczynski, the Unabomber, who was "the essence of evil" rather than a complex human being whose crimes might have been prevented. Most notoriously of all, there were the attackers of September 11, 2001, regularly spoken of not only as monsters, but as "animals" or "vermin" – and, of course, animals and vermin aren't entitled to due process.

9/11 marked the height of this very American tendency to push horrors beyond all understanding, as the philosopher Judith Butler argued in the months after the attacks. "We tend to dismiss any effort at explanation", she wrote, "as if to explain these events would accord them rationality, as if to explain these events would involve us in a sympathetic identification with the oppressor".

It's as if we think evil is somehow contagious. Instead of trying to understand why people do horrible things, we say that nobody will ever understand them, and that to try to makes you as evil as the killers.

With dire consequences. After all, if it were really true that terrorists and killers and rapists are fundamentally, irredeemably monstrous, then George W. Bush would have had a point. Kill the monsters, and the problem is gone. And there's an echo of this in the right-wing rhetoric of the past week, that the way to prevent killers like Holmes isn't gun control, or better psychiatric care, or rethinking the values of our entertainment industry – but rather toting semiautomatics to the movies, so that we can defend ourselves from monsters off-screen and on. In Colorado this week, applications for gun ownership spiked 41%.

James Holmes, allegedly, did something inhuman. But that doesn't make him non-human. Heinous criminals are people just like us, who through a complex network of causes (social, economic, psychological) reach a point at which they violate the order of things. If there is any hope of stopping them, we have to think much more deeply about how people become terrorists and murderers and rapists, instead of deluding ourselves that they are born evil. That may not be comfortable to contemplate. But it's the only way to live in something resembling society, and put aside the fear that there are monsters lurking everywhere.