Irving Bieber, before the homosexuals mugged the American Psychiatric Association and took over all the committees on the subject and began enforcing PC, did a longitudinal study of homosexual men in the late 1950's and early 1960's.
He looked at whether psychotherapy could help men who displayed homosexual behavior, which in turn involved some inquiry into the etiology of homosexuality.
Long book cut short, he concluded that about 1/3rd of homosexual men are "hard-wired" (i.e. "essential" homosexuals), while other groups display varying responses to attempts at psychotherapy and conversion therapy. He was attacked by the gay cabal, who tried to discredit him and terminate studies like his.
Nevertheless, in the 1990's, some 35-40% of healthcare professionals still believed, like Bieber and against the best propaganda efforts of the cabal, that homosexuality is primarily psychological (and therefore susceptible of psychotherapeutic amelioration).
The "essentialist" position is basically a lawyer's position, and not science; it's an argument the gay lawyer corps wants to push on the Supreme Court, that homosexuality is an "is", i.e. an essence (like black skin), and not a behavior or choice (and therefore subject to society's legislation and undeserving of the Supreme Court's highest standards of legal protection).
Interestingly, there are a significant proportion of gays who believe that sexual identity is "constructed", plastic, fluid, and changeable. Which means they are not on the same page as Lambda Legal, which will have somehow to keep them out of the courtroom.
I don’t understand the focus on root causes, from either side...
If homosexuality is innate, it does not necessarily follow that society must make accommodations for people with that trait. It could be an innate, but harmful trait to be treated, not celebrated, similar to the alcoholism gene.
If it is some sort of choice, it does not necessarily follow that society should not make accommodations for people who make that choice. It could be harmless, and a perfectly valid choice, similar to preferring vanilla to chocolate ice cream.
There are obviously other considerations besides its origin that determine the optimal public policies toward the issue. So, again, why the focus on root causes?