Why is one particular aspect of sexual preference singled out as (1) being ingrained from birth, rather than developing during childhood like every other aspect; and (2) necessarily being a core part of everyone's personal identity?
This just keeps being repeated, as if it's fact, but it's just not true. In fact, it's less true than the opposite conclusion.
It's been shown, repeatedly that toy preference, conflict resolution style, gender identity, and now even the genetic programming of the immune system are very different between the sexes, and exist at birth.
I'm not aware of any reason to believe sexual preference doesn't fall into the same bucket. In fact, wasn't this the entire basis of the gay rights movement?
The literature is extensive, and I don't have time to list all the references at the moment, but here's a couple to start off with:
https://en.wikipedia.org/wiki/David_Reimer
https://www.psychologytoday.com/blog/the-scientific-fundamen...
For further reading, you can browse through "The Optimistic Child" by Doctor Martin Seligman.
No, the basis for the gay rights movement was that being gay is not a justification for denying someone regular human rights. There are some people who only conditionally agree with this, if being gay is a way you are born and have no choice in it. There are other people who think it is repugnant to suggest that it is only ok for someone to be gay if they can't help it.