LOL.
Calling that nonsense a "theory" is like calling a tent a building, or a pair of roller skates a luxury sedan.
Homosexuality occurs in at least 70 non human animal species.
So it's obvious that (a) it's genetic and (b) it must have some survival benefit - to some individuals across a family / community group even if not to the fully homosexual individuals themselves ...
We don't know how it is caused. Because we don't fully understand the generation of sexuality in general, including the more usual heterosexual kinds. Something to do with brains and endocrine systems, but we don't really understand much of it ...
It is possible that there are underlying kinds of biological sexuality ... which are then restricted by social conformity. Maybe many more people could be bisexual. But we choose social roles; I'm fairly sure that's what happened in my own case. 'Choice' is a strong word, but I did successfully have penetrative sex with women when I was young, before settling as a gay man. Because it's easier not to have to fight it, and not to have to explain and warn.
It is about time that humanity grew up. Learned to respect and tolerate each other. Even to celebrate and admire diffferences. We are all facing the world together; we all face similar problems and threats. We are in danger from extreme ideologies and mismanagement of money, technology and power. So let's learn how to be happy, calm and safe with each other. Please.