Because self segregating black locales have the problem of depleted family structure the most. The results are disastrous. Allowing homo family arrangements only contributes to an existing problem.
You still have not explained what that has to do with gays and their children.
You're trying to compare single parent households to intact ones. That's way beyond apples and oranges.
I'm demonstrating empirically that kids need
both genders. Plenty of single mom homes in mostly black neighborhoods are essentially intact in the sense that necessary financial resources are there and opportunity for success still exists.
The problem is the kids lack that innately necessary gender role model. Usually it's a missing father.
Homo marriage contributes to that same problem by denying both gender role models in the home. It's very simple and the results are very clear. Just not convenient to those who want to push their self-focused and/or misguided agenda.