> I think "the big question" some people still have is whether being gay is perfectly fine or not.
I think this is very true and is a more fundamental question than what I've posed here.
Another way of stating my point is that the question of "innateness" allowed large swaths of the community to sidestep this question.
And this question is a very deep rabbit hole for the current cultural and political situation in the U.S.
Ask anyone who is comfortable in their sexuality whether they would be willing to take, say a course of therapy, that would change their sexuality. I think the majority would be unwilling, far more than the number of people who would be willing to sign up to a lecture that would promise to make them love the Simpsons. And I think that would be true for people who cherish, abhor, or are even indifferent to homosexuality (the exact proportions among those populations are probably different, but I suspect all of them would rise into the majority). There is of course, often due to mainstream pressure, many homosexual people who are intensely uncomfortable with their sexual orientation and wish to change it, but even taking them into account I still don't think they would make up the majority.
> Nobody will bat an eye if someone discovers they are straight after thinking they were gay.... What is objectionable though, is to try to force someone into a given sexuality, instead of letting them be and discover their sexuality in their own terms.
The problem is what counts as discovering their sexuality on their own terms. To borrow an example from one of my sibling comments, should schools be allowed to offer a gay conversion therapy course? Should schools be allowed to offer a straight conversion therapy course?
I suspect your answer would probably be "yes" if they're electives or both if they're mandatory, but this would already demonstrate how thorny of an issue this is. Nobody would care if a school only offered a "Simpsons' appreciation course" and not a "Simpsons' criticism course" or vice versa. (Of course the riposte is that sexual orientation, as a central component of one's identity, is a far more important topic, but there is yet another endless set of back-and-forths to be had on that topic). But the important thing is that these questions fade into irrelevancy if sexual orientation is immutable, but come immediately to the forefront if sexual orientation is mutable.
To recap my point is not to say that mutability of sexual orientation is the only big or even among the biggest questions, but to emphasize that it is a big question with many implications. To say that the mutability of sexual orientation is irrelevant is to miss a lot of the policy implications that hinge on its truth or falsity.
EDIT: A more apt comparison is probably religion, to the extent that you accept beliefs to be mutable. Should parents be allowed to send their children to religious camps? If yes, should parents be allowed to send their children to conversion therapy? If conversion therapy is too coercive, should they be allowed to send them to conversion camps? At what point does it become coercion?
All of these questions are very nicely sidestepped by immutability. No parents shouldn't send their kids to conversion therapy or conversion camps because they're ineffective and because they are ineffective at best they're a nuisance, at worst they inflict psychological trauma. But if they are effective then all of a sudden the parameters of the conversation shift drastically.