The idea that people can freely chose their sexuality is preposterous, paired with your disconcertingly accusatory diction (which I accuse you of) your comment leaves quite a bad taste.
http://www.bbc.com/future/story/20160627-i-am-gay-but-i-wasn...
Does this mean that every gay (or straight) person perceives their sexual attractions to be conscious decisions? No, but if you continue to insist that it's preposterous in the face of counterexamples, particularly counterexamples from gay people themselves, then I don't know how to respond to your outrage.
It's one thing to say, "Oh, I think such counterexamples are few and far between," but to say the very idea is preposterous just doesn't jibe with reality.
Bisexuals indeed have the unique opportunity to "decide" which side of their sexuality they pursue, because they enjoy both. That's what makes them different from "true" heterosexuals and homosexuals who can not enjoy both. (Though one could argue a homosexual forcing himself to have sex with a woman and make a family is not truly homosexual and we do know that's possible and happened quite often. I will leave that to the philosophers.)
Please keep in mind I am not even arguing for the "born this way" view. I have a "It does not matter" stance. I welcome ideology free research to clear it up though, but don't we already know the results? Both genes and environment play a role...
It’s not a growing trend to suggest people can control this. It is perhaps a trend that people acknowledge things change over time. Those two are not the same.