An interesting premise, m4m.
It will take me awhile to find the research without my professor's help, but the most recent studies indicate it is hormone levels in the womb which determine sexuality, and some mothers are more disposed to this combination of hormone levels (hence, not exactly a gene). Environment does play a part, but it is rather limited, except in extreme circumstances.
Back to the question- hell no I wouldn't be okay with that as the deciding factor for parents. Then again, I'm not okay with religious bigotry of any kind...
I wouldn't ask why some woman wanted an abortion, nor would I test a fetus for homosexuality. It is irrelevant.
I actually did a paper for an Academic Writing Class titled,
Homosexuality:
Is it caused by nature or nurture?
Being that it's 16 pages long, I'm certain it would go well past the post size limit (I think it's 500 KB). It's not groundbreaking. Basically, for the paper, you just chose argument/sources from both sides and pitted them against each other, then drew your own conclusion. But there were some interesting therories.
One source I found interesting was (copy & paste from my paper):
Dr. Anthony Bogaert (2006), a professor of Psychology at Brock University, Canada, theorized that male homosexuality can be traced to “fraternal birth order,” a theory which claims that it is more common for male homosexuals to be the youngest, or merely the younger, of the males having biological older brothers from the same birth mother. The theory is that a mother’s immune system remembers prior male gestations and, in an immunological response, reacts to newer male gestations as foreign, producing anti-male antibodies. The reason her immune system would not remember earlier female gestations is because she herself is female, thus any female gestations would not be reacted to as foreign.
Bogaert (2006) conducted a study using four samplings of homosexual and heterosexual men, three of which were from past studies, and one new study in which he recruited candidates himself in order to test and prove his theory. The results of his study showed more instances of younger homosexual men that had older male siblings from the same birth mother. The data did not show the same results for males raised in the same household with older nonbiological (step, half, and/or adopted) male siblings.
Bogaert, A. (2006). Biological versus nonbiological older brothers and men’s sexual orientation. Proceedings of the National Academy of Sciences of the United States of America (PNAS). Retrieved May 9, 2007 from: http://www.pnas.org/cgi/reprint/0511152103v1.pdf
Now, in my family, the two oldest (both male) are hetero. Then my gay brother, my gay sister, then me. So, we do fit into that theory. But that doesn't explain instances when the oldest in the family is a gay male. Interesting nonetheless.
OK, I know we're veering off topic slightly, but a good discussion is still a good discussion.