As Galland points out, "The social movements of the 1960s—black power, feminism, gay rights, sexual liberation—gave Marcuse a unique vehicle to release cultural Marxist ideas into the mainstream. Railing against all things “establishment,” The Frankfurt School’s ideals caught on like wildfire across American universities."source. This increasingly appears to be the advent of the social justice movement and political correctness as a major societal force in the west as we know it today.

Fast forward twenty five years to the 1990s, and it appears the Boomers who adopted the concept of social justice from the early 1960s to early 1970s have raised many (but by no means all) similarly-minded GenXers, who have already assumed their positions of power in the educational establishment - particularly the older members of Gen X. (edit - see Clemdane's comment below). This multi-generational emphasis on social justice is now bearing its logical fruits.

As the social justice movement swelled with the children and grand-children of the Boomers at the universities, the "revolutionary" nature of social justice began to fade despite continuing to be trumpeted as revolutionary. Indeed, tolerance of different lifestyles, the belief that race was largely a cosmetic difference and people should be paid the same for the same work became the norm. It was largely accepted that there was still work to be done, but most everybody was onboard. It was only a question of time until we were on the best path to a just society. The "revolution", for many, had achieved one of its most critical goals.

But the younger generation who had no first-hand experience of the rights movements of the 1960s, primed and ready to fight for "justice" by their parents, found itself with nothing left to fight for. This lead to an intensification of the criteria for "justice", not only should people be equal before the law, they should be equal in terms of how others view them socially and culturally (edit - see valued-customer's comment below). This means no matter what someone believed, it should be considered equally valid in keeping with the belief system that preaches subjective realities are just as valid as objective ones. Nevertheless, the white Christian hetero-normative paradigm retained its status as "oppressive" by the mere fact it constitutes the majority of society.

The caterwauling of social justice indignation today appears largely a form of hyperbolic virtue-signaling that was nascent, as best I can tell, sometime in the late 1980s with (comparatively) reasonable complaints about sexism and racism. When students were rewarded with increased social status for getting a peer expelled or faculty member fired, it incentivized others to do the same. Accusations of "mere" sexism and racism are hardly capable of raising an eyebrow anymore, though still more than sufficient to get people fired. This has resulted in an ever sinking threshold for inappropriate behavior and an ever increasing intensity in the degree of virtue-signaling. Enter microaggressions.