Jon Haidt in Why the Mental Health of Liberal Girls Sank First and Fastest:
There was a culture that was encouraged on Tumblr, which was to be able to describe your unique non-normative self. That’s to some extent a feature of modern society anyway. But it was taken to such an extreme that people began to describe this as the “snowflake” (referring to the idea that each snowflake is unique), the person who constructs a totally kind of boutique identity for themselves; then guards that identity in a very, very sensitive way; and reacts in an enraged way when anyone does not respect the uniqueness of their identity. On the other side of the political spectrum, there was the most insensitive culture imaginable: 4chan. The communities involved in gender activism on Tumblr were mostly young progressive women while 4Chan was mostly used by right-leaning young men, so there was an increasingly gendered nature to the online conflict. The two communities supercharged each other with their mutual hatred, as often happens in a culture war. The young identity activists on Tumblr embraced their new notions of identity, fragility and trauma all the more tightly, increasingly saying that words are a form of violence. Meanwhile, the young men on 4Chan moved in the opposite direction; they brandished a rough and rude masculinity in which status was gained by using words more insensitively than the next guy. It was out of this reciprocal dynamic that today’s Cancel Culture was born in the early 2010s. Then, in 2013, it escaped from Tumblr into the much larger Twitterverse. Once on Twitter, it went national and even global (at least within the English-speaking countries), producing the mess we all live with today.