I'll stick my neck out on this and even accept any bashing and shouts of hypocrasy, bigotry or whatever.
I don't have any issue with being gay (insert cliche that some of my best friends etc). Sexuality doesn't concern me, doesn't shock me, doesn't enter into my thought process. It's who you are, same as they're short, tall, dark, fair, etc.
But, if I had a preference would I prefer a child to be "straight"? Yes. Is this because they'll face prejudice and I want to protect them? I'd love to say yes it is. I'd love to keep my liberal, accepting, understanding, inclusive, diversity tag and say any reservation would be because I didn't want my child to suffer any harm. But that'd be a lie, it's because I just would prefer them to be straight.
I know if they were gay I would support them and it really wouldn't bother me or affect my relationship, but if the question is "preference", I'd prefer them to be straight. I could spout some pseudo-scientific justification that it's because being straight means I have a greater chance of my genetic material passed on for another generation. Yeah, that's it, genetic material. But no, I'd just prefer them to be straight.
Maybe there's a psychoanalysis argument that it's to do with "sharing" things as father and son or whatever, maybe Freud would suspect latent, hidden stuff deep down.
It's completely hypocritical, it's completely against my own moral compass, I disgree with michaelm's views on the nature of being gay, but I stand by my preference.