I like this guy and he's a good counterexample to the idea of "children raised in same sex marriages cannot be functioning members of society." Unfortunately, he's broadening the conclusion to "same-sex are every bit as good as straight parents" which is a fallacy of argument from final consequences. His status in no way affirms the premise. It's like walking through a field, looking down at your legs, and saying "they're still here, so there must be no mines buried there." It could be the path he took, maybe a mine did go off and didn't affect him in an obvious way, etc.
Now, the evidence as far as I'm aware of it, actually does indicate that there isn't serious harm done by same sex parenting. I support full adoption rights for gay couples and don't think they should be discriminated against for their orientation, but I also think it's important to point out arguments that are at their core illogical even if they promote things you believe to be positive.