Not really comparing like with like here. If there is a legitimate and sensible reason to believe that two people are unable to provide adequate care for a child then they shouldn't be entrusted with that care. A legitimate reason would be that the two parents need extensive and ongoing care themselves. I don't think that most disabled people fall into this category, e.g. blond and deaf people are often quite capable of managing on their own with minimal help. But those that do ought not to be allowed to adopt. The important thing is to look after the best interests of the child.
There has been a campaign in The Times, and perhaps other newspapers as well, to change the guidelines for adoption to allow adoptive/ foster parents to take in children of a different cultural background from their own. The councils have felt, perhaps with some good reason, that the cultural clash could be damaging for the child. I'm not so sure that this is a legitimate reason not to allow an adoption, as the council's care system can't provide the right cultural environment either and two loving parents would be far better placed to adapt their lifestyle as needed to suit the child.
Anyway no, it's not like with like at all as compared with same-sex parents. There are legitimate reasons not to allow some disabled couples to adopt. It is becoming increasingly clear that there are no such reasons to deny same-sex couples the right to adopt.
Minor aside, Sharingan: "its", not "it's", in the possessive case.