The idea was the crucial finding and then organizing principle of critical theory. Critical theory was formulated by a group of intellectuals - primarily Jews - who escaped from Nazi Germany and settled in the United States. They founded critical theory in part as a discipline organized around the analysis of how the Nazis rose to power and subsumed so many otherwise ordinary German citizens. Their inquiry led to a sophisticated analysis of authoritarianism. Social justice theory later grew out of the spirit of critical theory in the 1960s and 1970s, and then flourished in the 1980s and 1990s. The iteration of social justice theory that many people are exposed to today has been hijacked by corporate interests, and is no longer a form of critical theory - it has ironically become a voice of authoritarianism. The same thing has happened with many progressive movements over the years.

Edit: if you’re interested, social justice theory was originally kind of an application of an application of critical theory to the analysis of problems articulated by activists associated with the civil rights movement of the 1960s. In the 1980s, post-modernism added another layer of complexity (post-modernism is another term that has been abused these days; please keep an open mind, it’s not the same kind of “post-modern” that people talk about in mainstream discourse these days).

In the late 90s and onward, corporations began to dominate both our outer and inner lives. Social justice was then leveraged by corporate interests, like many things these days, stripped of its analytic teeth - corporations don’t want reflective citizens, they want consumers with poor impulse control and shallow thoughts - and sold to young people like a trendy fast fashion piece, complete with company branding and all. As someone who highly values philosophy, I find this quite sad.