It goes back to Rudi Dutschke
All of this nonsense goes back to Rudi Dutschke - a leftist German scumbag who (in the 1960s) urged the Left to mount a "long march through the institutions" - teacher training colleges, schools, universities, media, government - infiltrating and subverting them to push the Leftist agenda.
The Left knew a powerful idea when they saw one and they grabbed this idea like a drowning man would grab a life-raft.
Fast-forward 50+ years and we can see the results. Pronoun nonsense. Universities pumping out SJWs and snowflakes who know nothing except how to be "offended". Schools pumping out children who are terrified that the world will erupt in flames in a couple of years.
This pronoun nonsense at Stackexchange is nothing but a **leftist power grab** to control yet more of the English language. It is THAT simple.