Warning of imminent ecological catastrophe, the Earth Liberation Front became notorious in the late 1990s for setting fire to symbols of ecological destruction, including timber mills, an S.U.V. dealership and a ski resort. The group was widely demonized. Its exploits were condemned by mainstream environmental groups, ridiculed by the media and inspired a furious crackdown from law enforcement. But in 2022 the group is more relevant than ever. These days even America’s mainstream environmental movement has begun to take a more confrontational approach, having previously confined its activities largely to rallies, marches and other lawful forms of protest. Even the “staid” environmental groups based in Washington have slowly started to embrace more radical tactics. Climate activists are starting to abandon their dogmatic attachment to pacifism, choosing instead to work toward destroying the “machines” inflicting the damage — but will such a radical idea prove effective? The journa...