In October, a 19-year-old army private called Danny Chen climbed into a guard tower in Afghanistan and shot himself in the head. According to the Chinese-American soldier's relatives, his comrades had subjected him to a painful process of "hazing" and racial abuse, including pelting him with stones and ordering him to do pull-ups with a mouthful of water, which he was prohibited from spitting out or swallowing. In a surprise announcement on 21 December, the army announced that eight of his comrades would be charged for offences ranging from assault to involuntary manslaughter.

This was the second such case in six months. In August, three marines were charged with mistreating another Chinese-American soldier, Harry Lew, who killed himself while stationed in Afghanistan. Lew, who had allegedly been stomped, kicked and tormented, was found dead in a foxhole that he had dug for himself. He had written on his arm, "May hate me now but in the long run, this was the right choice. I'm sorry. My mom deserves the truth."

Racism and bullying in the military are nothing new but for those outside the US, the concept of hazing rituals is hardly explicable. In the 2004 book The Hazing Reader, edited by Hank Nuwer, Stephen Sweet lists incidents of college students harmed or even dying while pledging to join fraternities: some were buried alive, others were shocked with electrical charges or pressured to drink far in excess of their capacity. The willingness of young men and women to submit themselves to degrading and sometimes dangerous acts, designed specifically to humiliate them, is as bizarre as the willingness of others to inflict such cruelty on their peers, colleagues or comrades. Is this a uniquely American predicament, and if so, why?

Hazing is all too easily explained (and even justified) as a means of cementing bonds within a group - but surely underlying any sense of belonging that it may induce is the assumption that, for those bonds to matter, a species of isolation from others not initiated through the ritual is necessary. To enter into a group through hazing is, in effect, to step out of the rest of the world and its rules. Or, at least, it is to position yourself as a member of a chosen people, separate from the rest. In many ways, it is a natural, microcosmic extension of that particularly American notion of exceptionalism: ever since the Puritan lawyer John Winthrop delivered his 1630 sermon exalting America as a "city on the hill" upon which the "eyes of all people" gazed, the nation has believed in its own otherness, even as its culture and political power grew more and more dominant across the world. The frontier is where it all began and the mythology of the United States remains rooted there.

The "true" American must play the role of the outsider: the Davy Crockett, the Billy Bonney. Look to the Tea Party or the Westboro Baptists - each group is besotted with its own outlaw fantasy. Yet to be a genuine outsider is unthinkable. Dan Choi, an Iraq war veteran who was forced out of the army under "don't ask, don't tell", recently told Public Radio International that being an Asian American in the military was a lonely experience. Racism was rife but he endured abuse in order to "fit in": "I wanted to joke and make other people feel comfortable . . . In the army, you're taught if you stick out, there will be consequences. If you look different, you're starting off with that additional burden."

Seen in this light, Chen's hazing and its outcome are more complex than yet another "isolated incident" of needless cruelty, as Martin Dempsey, chairman of the joint chiefs of staff, insists. Humiliation has long been used to establish or normalise social relations; indeed, the social scientist Evelin Lindner pointed out in 2006, "In the English-speaking world, humiliation was not seen as hurtful until about 250 years ago." "For millenia," she wrote, "people believed that it was normal and morally correct to have masters and underlings." In hierarchical environments such as the military, this power relationship is bound to be more pronounced than elsewhere. Ten years before Lindner, the social psychologist Alexander Durig described the "mind of the individual" as principally motivated by "fear [or] need of humiliation . . . We often learn to respect those who humiliate us. Conversely, we often learn to humiliate those who respect us."

Chen, like Choi, seems to have initially taken the abuse hurled at him on the chin. This was the army, after all. In a letter to his family, quoted in the New York Times, he wrote: "Everyone here jokingly makes fun of me for being Asian." In another: "People crack jokes about Chinese people all the time; I'm running out of jokes to come back at them." After his suicide, a Pentagon spokesman said that soldiers "treat each other with respect and dignity" but this platitude rings hollow. What to the insider are "jokes", to the outsider - the ethnic minority, the gay man, the lesbian - can be slow psychological torture. The US army claims that hazing is prohibited and insists that there is no racism in its ranks but the activist Kwong Eng seems correct to argue that "the culture allows it to happen".

Researchers have shown that those who perceive themselves to be targets of bullying experience high levels of stress and are less likely to trust the established avenues of redress. With little prospect of official intervention, Chen no doubt felt compelled to play along. Maybe his fellow soldiers saw the brutality they allegedly inflicted upon him as a form of initiation ritual. Maybe not. Yet the fearful desperation of a culture that requires such horrific customs has, once again, been dragged out into the light. Eight men are being charged but the issue cannot be resolved through the punishment of scapegoats alone.

The incident has been presented as a crisis of poor discipline. It is also, on some level, a crisis of national values and identity. While US popular culture glamourises the outsider, many are terrified enough by the prospect of being at the bottom of the social pecking order to assert their insider status by humiliating - literally, "bringing to the ground" - weaker peers. Bullying and racism are not unique to American culture but in few other nations is the question of belonging so central an anxiety.