The word homosexual also emphasizes disease and disorder. The word's roots in clinical diagnosis of a mental illness are why gay people in the anglosphere rejected it in favor of our own, mental-illness-free label.
I'm surprised this guy doesn't know that, or if he does know, that he doesn't care.
But then, he's clearly not a thoughtful or well informed person.
His notion that queer communities started embracing/accepting trans people only about 15 years after the turn of the century is just ... Well, as you demonstrate, it's just nonsense.
I should know. I was member of NYC's Queer Nation in 1990. I listened then to queer leaders talking about the inextricable intertwining of gay and trans communities. I watched knots of people press around Marsha Johnson at the LGBT Community center, hanging on her words.
I lived the reality that Queer Nation and the Pink Panthers were working to stop street violence, much or most of it directed against gender nonconforming people.
I lived the reality that vocabularies were slowly changing, that "gay" was no longer an umbrella term like queer is today but that many people (including Marsha) still used it as an umbrella term.
This author seems not to understand any of that. Or if he does understand, he so thoroughly dislikes trans people that he's ignoring what he knows.
Honestly, though, he just seems ignorant. How do you get a book published that's so factually wrong, I wonder.
Neat trick if you can pull it off, I guess.