There's no nicer way to say this but...

[Reforged]

Scenario:
Homosexuals marry, they adopt kids, as a result overpopulation drops, unwanted children are given loving homes which would otherwise be impossible for them to obtain and hate crimes become even more unacceptable in modern society due to the promoted ideal that different doesn't mean inferior.

Please explain, using evidence to back-up claims, how this would constitute the destruction of a stable society.
Good luck.

I call it bullcrap. Adoption by gays does not solve the overpopulation problem. Family planning solves overpopulation. Openly homosexual couples are not part of it, due to their inability reproduce.
Family planning solves the core problem of unwanted children. If such children do not exist, there would be no need to adopt them. Besides, for homosexuals, this is only the beginning. I'm fairly certain that gays would rather have children via surrogacy than adoption, as we can see from Elton John, who chose to obtain a child via surrogacy, and I can tell you this, here and now, that surrogacy will be a major business enterprise in the future, if the ridiculous demands of the homosexuals are met today.
How about this scenario?

Unrealistic.
It was never implied adoption would solve overpopulation, the fact they can't have kids themselves would. As to the problem of surrogacy, discourage it. Not just to gay couples but to straight couples as well, encourage them to adopt instead. Adverts, billboards, it doesn't matter. As long as its being put out there that the kids need homes, make it look like the right thing to do. That a child doesn't have to have your genetic traits to be your son or daughter, it just needs your love. These aren't unreasonable concepts. Also, I think it highly unfair that you use Elton John as the standard by which all gay couples should be judged. Most of them have their own hair and everything.