The "homosexuality is a birth defect" argument has some supporters but so far, they can't offer a medical treatment or prevention, so it's worthless as a way to deal with the fact of homosexuality and bisexuality.
Kinsey, the sexual researcher, found that human sexuality is on a continuum. Most people are neither 100% heterosexual or 100% homosexual, suprisingly enough.
That's why a society who sees sexuality as "two choices" is scientifically ludicrous. Our own sexual behavior informs us otherwise.
Kinsey discovered that many people who identify as primarily heterosexual have occasional mild to strong homosexual urges, fantasies and behaviors.
And people who identify as primarily homosexual have an occasional heterosexual urge, fantasy or behavior too.
I have a young gay friend who admitted to me that he about died once when he discovered that watching Uma Thurman in "Kill Bill" got him aroused. It totally freaked him out that a WOMAN did that to him and I had to assure him it was normal. It didn't mean he wasn't gay, or mainly attracted to men.
But, it demonstrates why people can fake being straight or genuinely experience an attraction for them that isn't their usual one, and that makes them believe they are "cured" of homosexuality. Or on the other side of the coin, "OMG, am I GAY NOW??"
Our society is so homophobic, some straight guys have a hard time admitting that certain situations, they get an occasional homosexual ping too.
Other societies view that as normal and even allow people to play around or experiment with it, and get it out of their systems, but in Western culture, one homosexual act defines you for life, especially for males.
A lot of primarily heterosexual males are shamed into denying any homosexual experimentation, but people are going to end up being what they are, so we need to learn to relax about it as a society. And yes, some people will find themselves in the middle, experiencing attraction for both sexes. Also perfectly normal.
I've been a sex ed teacher for many years now ,btw.