You said "we just don't know" what the consequences of gay parenting may be - but even with a conventional family comprised of a male parent and a female parent who are married/defacto, you just don't know how that might turn out, either. I don't think anyone needs to point out that even conventional families can have utterly catastrophic outcomes. I would have prefered anything to the family situation I had to suffer through between the ages of 9 - 15. Being raised by a single parent, gay parents, divorced but sensible parents, whatever - they would have all been so much better. At least then, I wouldn't have have been left with the desire to erase a huge chunk of my memory.
All a kid truly needs is someone (it doesn't really matter who) that loves, nurtures and supports them and provides a stable home. In my opinion, so long as a child's got that, there won't be any long-term consequences that you can't deal with.