The guy has a lot of documentation for where this all came from out of nowhere. I bought the book and it's fascinating how much documentation the guy has on how the whole thing got astroturfed in no time. I don't know how old you are, but before the early 2000s, the only place that I ever encountered "transexuals" was in San Francisco sex clubs. Then all of a sudden, in the span of less than 10 years they're everywhere. How the heck did that all happen? Reading through his research is a really interesting deep dive into how to bootstrap a radical cultural change from scratch.
Edit for context since OP has edited his comment without acknowledging it: Where it now says ""transsexuals"" it said "trannies" before.
No one ever starts a sentence with "The Jews control" and ends it with "the home owners association on our block and have done a phenomenal job managing it."
No one ever says "The Japs" followed by "have really contributed to our culture in the form of anime".
No one ever says "that n***" followed by "is an inspiration to us all and we are proud to have him in our community."
No one ever uses the word "tranny" followed by something well thought out and respectful of transexual people.
None of these words/phrases have an offensive dictionary meaning, but they are all rightfully associated with offensive speech.
It's usually the first if referring to familiar people and the second if referring to strangers. Even exactly the same word can cut both ways. "Dear" is affectionate towards family members, calling a coworker "dear" is condescending.
Also, as other posters have said, rule-based logic can only get you so far. It's all in the context.
A gay man might jokingly call himself a poof (or one of his straight close friends might in the same vein based on a mutual understanding), but again, you don't use such words in a polite, neutral setting without coming across as a very nasty person.
Some women are trying to reappropriate the word 'slut' from its negative connotations (cf. The Ethical Slut, Easton and Hardy, 2009) and some use it proudly, but again, anyone calling any woman who has an active sex live with more than one lover a slut will be met with derision.
This is no different.
The way I remember the pre-2000s there was definitely mention of trans people in popular culture. The big difference is being trans was being treated as the punchline, or otherwise derogatory. (The first example that comes to mind is Tone-Lōc's 'Funky Cold Medina', and also that Aerosmith song https://www.songfacts.com/blog/interviews/desmond-child)