gay couples' right to adoption
This is a highly debated area. the supreme court employed a rational basis + a bite test in sexuality related cases, e.g. Lawrence v. Texas. But when it comes to adoption, I believe at this point in time, a pure rational basis test is adequate. First, to decide what level of scrutiny to employ, we must decide what's the source of this right or privilege. I guess it fits under either liberty or equal protection and therefore it follows all the classification and class legislation procedure. But one thing central to the distinction here is that the very basis of this classification IS central to the goal of the legislation against gay adoption. you could argue that one's gender has nothing to do with one's performance in the military and therefore it is over inclusive and under inclusive in the sense that it disallows an opportunity which should have been afforded to them, and under inclusive for allowing the men that do not meet the military requirement an opportunity for access.
But in this very case, I believe the key is that a gay couple would deny a kid's right to have both a father and a mother in the same household, helping to bring him up. Single parents who are straight at least have the potential to make this happen, whereas gay couples deny this opportunity to the kid from the outset.
This is not to say that a family with two fathers (or mothers) are inadequate for the upbringing of a kid. This is to say that at this point in time, I haven't seen enough evidence to show that there is no noticeable difference / impact on the kid.
In other words, you are doing a social experiment on the kids by placing them in gay couples' households. It might be worse for the kid, or no noticeable difference, or even better for the kid. IT could be many different things, but I simply do not know if there is going to be any systematic negative impact on the kids.
You could argue that serial killers are equally bad as an adopting parent, but that is logically irrelevant to this argument. there are gay serial killers too. the gay population basically has one extra dimension compared to the rest of the population. and we simply don't have any information to decide what that new dimension is going to mean.
I think we should stick to the proven model (let a heterosexual couple adopt) and wait a few more years before we are more sure of the impact on the kids before we undertake unnecessary risks with these children's lives.

