What forms of protest are legitimate? And when does protest become terrorism?

Suicide bombing falls firmly on the latter side; roadside picketing, on the former. For all the debate and opposition it has engendered, there’s little controversy on the legality of Occupy Wall Street. Many more Americans favor the protests than disapprove of them — the numbers vary widely between polls, but in most, supporters outnumber denigrators by about two to one. Given the nation’s political divisions and the less than explicit platform of the movement, it seems that such national solidarity reflects less a sea change of public opinion and more the growth of an inchoate malaise.

We are living in an era of civil unrest. It may have begun in the Color Revolutions of the former USSR, or in the smoldering discontent of Europe’s immigrant banlieues, which erupted most significantly in Paris in 2005. It has drawn on tools and vocabularies as diverse as the Internet and the Intifada. The current wave was inaugurated in the streets of Tehran, and its most dramatic expression came just last week with the death of a brutal dictator at the hands of those he oppressed.

Unlike previous periods of revolt — 1989, for example, or 1848 — this one has had a strangely NIMBY quality, with governments cheering on the oppressed masses of other lands until the mobs appear at their own gates. Sometimes it has been brutal, sometimes inspiring, and often both at the same time.

In this country, at least, the supporters of these uprisings tend to be pacifists. We tend to cheer on nonviolent marchers, decry police retaliations and search every movement for the shadow of Gandhi or Martin Luther King Jr. We question the morality of violence committed for any cause and often forget that the most potent engines of protest — oppression and martyrdom — ­run on death.

We forget the militaristic connotations of the verb “occupy,” a word that sums up so many global wrongs that I doubt the ability of any cause to reclaim it in the name of international justice. Occupation is perhaps the most extreme form of illegitimate government, but also one of the most intractable. Lines drawn on maps harden over time.

On Tuesday, reports surfaced that the 10th Tibetan monk this year had set himself on fire. Why it took an even 10 to attract widespread media coverage is one question; why the Chinese government labeled the immolation an act of terrorism is another.

Answering the first meaningfully is beyond the scope of this column. Suffice it to say, I think it has something to do with the trendiness of activism, which works wonderfully when a given cause is in vogue and is downright poisonous when certain subjects fall out of fashion.

“Free Palestine” is ubiquitous across bumper stickers, college campuses and billboards. “Free Tibet” is an oddity, confined largely to New Age shops and roadside cafes in Northern India. If I saw another student at Yale sporting the rising sun and snow lions of the Tibetan flag, I would assume it was a thrift store purchase with no more significance than a Beastie Boys t-shirt from 1987. Whatever your stance, on either issue, it is curious to me how the entirely unresolved question of Tibet drifted out of fashion, to be replaced by a fixation on a strip of land that is undoubtedly important but is about as large as Massachusetts.

As for the second question, I wonder in what way self-immolation is an act of terrorism. How does it differ from, say, a hunger strike? It is more gruesome, certainly, and it occurs most often in public, not behind the closed doors of a detention facility. Visually and psychologically, it spreads fear. It communicates desperation rather than resignation. Accounts of the Tibetan immolations note the strong taboo on suicide in most Buddhist sects, highlighting the extremity of the act on the part of a believer. All these angles recall the ideology of suicide bombing, and so the uncomfortable question arises: If a suicide bombing is intended to kill only its perpetrator still an act of terrorism?

Any form of protest that creates its own martyrs must be suspect. As this era of unrest continues, those who champion the oppressed must examine which acts they are willing to celebrate and which must always be condemned. At the root of this soul-searching lies the question of how much violence can be tolerated in seeking the destruction of entrenched and oppressive orders. In confronting the injustices of the 21st century, pacifism and activism may be on a collision course. It will take a new kind of leader and thinker to see if they can be brought to concord.