As someone who intends to become a parent at some point, I want my hypothetical children to have the best possible life as I understand it. That means, among other things, that I want them to have best possible genetic traits so that they do not begin their lives already at a disadvantage. I will use any means at my disposal to ensure this.
Hopefully, by the time that my children will reach puberty, homosexuality will not carry the stigma that it does today. However, even without the vast social disapproval-- which I do not think will lessen considerably by then-- homosexuals are still disadvantaged by a smaller pool of sexual partners and considerable inconvenience related to reproduction.
If there were something I could do-- without harming them-- to ensure that my children did not bear such a burden, of course I would do it. Since they are not my children until they are born and named-- and I am named their father-- then aborting fetuses with this trait accomplishes that goal.
I wish the technology were better. There are traits I am far more concerned about than homosexuality that I would like to protect my children from.
Of course, I do not think homosexuality is genetic. My suspicion is that it is caused by prenatal hormone changes-- and I do not know if it even could be detected prenatally.