Keith: I think it very likely that a genetic cause will emerge.
People will then have to decide if it is a genetic "defect" and if parents will be allowed to make choices about the sexuality of their babies.
This is the current position with Down's and other conditions.

I agree with you about the genetic component. I'm interested in your opinion: Do you think that society should move to "treat" (by which we mean, in the short term, to abort) a feotus that displays a genetic trait, which of itself causes no harm or prejudice to the life that follows that could not be prevented by people just being nice and showing respect to each other?

We are coming back to Eugenics aren't we? Prejudice and bigotry harms people, so rather than stop prejudice and bigotry, let us just cull the victims? Would that be a better world for anyone? Where do you stop with the list of victims that should be culled?

The Down's analogy is a poor one, I hope that you will reconsider it. Parents receiving an in-utero diagnosis of Down's have an agonising choice to make (whatever they decide), but they have to make it because their child may be utterly dependant on constant, life-long, painstaking care and financial and material resources in order to realise their potential.

Whereas a gay person just requires people not be nasty.

For the record, I believe that abortion is problematic and too freely resorted to. I don't believe that Down's is necessarily a reason to abort a foetus - I have known too many people with Down's syndrome who are just wonderful people leading good lives with the right support and care. But I recognise that people struggle to make difficult choices and they must be supported to make and live with those choices, whichever one they made. All choices have consequences, and the decision by a couple to abort a pregnancy they hoped would be a cherished child must be absolutely heart-breaking for them.