The week of President Donald Trump’s inauguration, thousands of Americans used civil disobedience to disrupt events. An LGBTQ dance party raged outside of Mike Pence’s house. Iraq Veterans Against the War occupied John McCain’s office in opposition to Rex Tillerson’s nomination. On Inauguration Day, Black Lives Matter activists blockaded security checkpoints. Democracy Spring activists interrupted the swearing-in ceremony. Code Pink marched around the National Mall in a colorful pack. An elderly Asian American woman gave a middle-finger salute. The day after inauguration, millions of people participated in the Women’s March on Washington at its Sister Marches. Hundreds of thousands have remained active in pro-immigration protests and other rallies in the weeks since then.

At the same time, there’s been a reemergence of “black bloc” tactics: Protesters who incite property destruction and street fighting. The week of Trump’s victory, police in Portland, Oregon, fired rubber bullets against largely peaceful demonstrators after black bloc provocations. The more than 230 people arrested in D.C. over inauguration weekend—most of them associated with black bloc actions, which resulted in a burned limousine and vandalized storefronts—drew the coverage away from thousands of people using civil resistance. And at U.C.-Berkeley last week, 1,500 people peacefully demonstrated against a planned speech by right-wing Breitbart writer Milo Yiannopoulos, later to be joined by some 100 “masked agitators” who started a fire, hurled rocks, and attacked other protesters.

Defenders of black bloc tactics, which also include rioting and “Nazi-punching,” argue that these actions are necessary and legitimate against powerful opponents. They believe such tactics help to protect nonviolent activists—particularly those from marginalized communities—from militarized police. Property damage, street fighting, and fires draw more media coverage, they argue, and participation in violence can deepen activists’ commitments and embolden nonviolent protesters to be more courageous. But they also believe that appeals for nonviolent action are for the privileged and the sell-outs. Of calls for peaceful protest, one defender of black bloc actions said, “That kind of argument can devolve into ‘just sit on your hands and wait for it to pass.’ And it doesn’t.”

On balance, though, black bloc tactics often hurt the causes that these activists claim to be fighting for. While violent flanks have sometimes produced short-term tactical advantages, they often come with painful long-term costs for movements seeking change—and the communities they purport to represent. The historical evidence in support of this conclusion is worth considering as the Trump resistance builds.

Expert practitioners of violence know that to truly suppress dissent, they must win the larger political struggle for legitimacy. One does not compete for legitimacy at the ideological extremes, but rather, at the ideological center—an audience generally unpersuaded to take up violent tactics to follow masked vigilantes into an unknown utopian future. Leaders need a pretext to convince the center that a major crackdown of dissidents is required. Historically, states have easily exploited the appearance of violent flanks to re-assert their legitimacy and suppress larger nonviolent dissent.