Trey(Trevor is adult name, Trey young nickname) always was shy. You might not ever realize that if you saw his presentation as an adult; however, he learned many coping mechanisms (masks that everyone wears to various degrees) that could "cover up" his insecurities.
I guess what started the self-hate was Trevor's constant questioning, doubt , and searching to "fit in".
As he aged he got less comparing himself to other people for so many reasons (to be explained later *).
But in summary, when you are in your seventies, and you have perhaps less than 10 percent of your life left, what could be the "big deal" or "return on investment" of even trying to be like anyone else?
Whether inborn or learned, Trey figured out he was in automatic competition with his brothers, if for no other reason than when he got to almost every grade in school, teachers who had both Spectre Jr. and KJo commented or implied "are you going to be like your brothers?" Even KJi was great at baseball and art.
Also Trey had poor vision and eventually got glasses when in elementary school and later on in life,he was finally diagnosed with a semi-functional eye problem of being unable to triangulate on objects (meaning no ball catching or throwing for him without plenty of embarrassment from brothers or peers.)
Ironically, on his own, Trey/Trevor figured out by wrestling in high school/college, gymnastics/running in junior high or swimming (learning at about 22 years old) that he was more than competent.
Above and beyond all, trying to figure out his sexuality was and is a constant mystery and challenge to him. (see the "coming in and out of the closet" routines/adventures chapter). By default the Church he had automatically attended due to parent and regional "indoctrination" (not meant in a bad way but it is what it is) put tremendous guilt and shame upon him. Now when you consider he felt he was in competition from the get go, and he could not see to catch or throw a ball accurately (which most youth are competent to some degree), and being more understood by his mother than father (see the chapter on the bullfighting Dad) he subsumed the stereotypical "gay" profile without even acting out on it.
To add to the self-hate was the common early society concept of gay people being child molesters and that they "have to recruit". What a burden!
Side note: At some point a research item had pointed out that the "gay" brain is different than other brains which seemed to help Trevor at first accept himself that it was "beyond his control" if wired that way.
However, "which came first, the chicken or the egg" doubt is a struggle which even people with PTSD wonder, was my amygdala large and my hippocampus small to begin with (more prone to PTSD) or was it caused by PTSD. Same struggle with Trevor.