What you are saying is, because some heterosexuals fail, there should be no standards at all, and no one should be allowed to tell the politically incorrect truth that gays as a statistical group do not produce as high a percentage of well-adjusted children. You are ignoring the natural rights and needs of the defenseless child in favor of indulging the desires of the gay adults.
What's your source on this?
I am not willing to dismiss the arrangement outright if there are cases where the situation produces children than a traditional situation. And, what are these standards that you speak of? If the gay people are capable of doing a better job than the straight that's the only standard that matters. Perhaps we should also look at black people and their aggregate stats on parenting. Maybe we should outlaw them from procreating due to their rates of illegitimacy and all the problems that go with that? Maybe we can find some other groups to ban from having kids because they don't meet someone else's standard?
Where does it begin or end?