This phrase is inextricably linked to the Great Proletarian Cultural Revolution (文化大革命, Wénhuà Dàgémìng) from 1966 to 1976. While the phrase existed before, it was Mao Zedong's endorsement of it that ignited a firestorm. He used it to empower the Red Guards (红卫兵, Hóngwèibīng), legions of radicalized students, to challenge and overthrow anyone and anything deemed part of the “old” world or counter-revolutionary. This included teachers, intellectuals, government officials, and even their own parents.
The slogan served as a moral blank check for extreme actions, legitimizing the destruction of cultural artifacts, public humiliation sessions (known as `斗争 (dòuzhēng)` or “struggle sessions”), and widespread violence. For this reason, it is a deeply sensitive and painful phrase for generations who lived through that era.
Comparison to a Western Concept: A common Western slogan from the same era is “Power to the people.” While both slogans challenge established authority, the difference is profound. “Power to the people” was a grassroots, anti-establishment cry against the state. “造反有理,” in stark contrast, was a call for rebellion sanctioned and encouraged by the supreme leader of the state itself (Mao), directed inward against perceived enemies within the country's own institutions and social fabric. It was a top-down revolution masquerading as a bottom-up one.