I don't argue for a genetic source. The theory of too much or too little hormones during pregnancy makes more sense.
That would explain why so many female athletes are lesbians with male traits usually not associated with your average female.
It would also explain why so many male homosexuals have effeminate traits.
Obviously, perverse behaviors can be learned, but the idea that people learn to be attracted to the opposite sex is baloney. I was raised in a strict religious environment where even thinking about sex outside of marriage was considered a mortal sin.
But as boys enter adolescence, they become very aware of the opposite sex even when they are warned about severe post-life ramifications of thinking "impure" thoughts.
That's just basic hard-wired biology. No urging was needed.