I am always a little disappointed when a gay friend tells me that he doesn't think that gay people should be allowed to adopt children and then start reiterating the usual arguments - "A child should have a mother and a father", "They'll get bullied at school - they shouldn't have to be part of someone else's social experiment".
I've met very very very few gay men who want to adopt kids. The ones who do, and go through with it will have been subjected to intense scrutiny by adoption agencies and would have had to undergo an awful lot of soul-searching and justification. They'd really have to WANT the kid. And I think that would make up a great deal for the kid not living with a traditional mother AND a father. The amount and quality of love and care that you get is much much more important than who is loving you. If it were up to me, I'd probably exclude about 80% of heterosexuals from having children - so many people don't even seem able to look after themselves properly, and I've grown very tired of seeing selfish parents, out with their kids - who clearly don't want them around, doing their best to ignore them, except to tell them off in a bored, brittle voice.
And since when did all children start living in loving, stable family units that have both opposite-sex parents living together anyway? Many kids are already involved in some sort of "alternative" social experiment involving single parents or step-families - but I never hear anyone complaining about that (although they did in the 1950s - until a few people started saying "fuck you bitches - I'm doing it anyway so get over yourselves." - social change can only happen if someone is prepared to be brave.) Admittedly, it would be hard to see a child bullied for having gay parents - but kids will always find a reason to bully someone if they feel like it. And hopefully, having a gay parent should help make the child more tolerant of diversity. The problem here is the bullying (which needs to be stamped out), not the gay parents.
No, the reason why some of my gay friends don't approve of gay adoption is due to their own internalised homophobia, coupled with disinterest - they either can't see themselves in a relationship or caring for a child in the near future so why make it legal?
Fortunately, a poll on OUTintheUK earlier this year put 85% of gay people in favour of gay adoption. So the naysayers are at least in the minority.