I'm not supporter of gays. But if we live in democracy, then ok, let it go - allow gay marriage.
But I'm strongly against that they would able to adopt kids. I try to explain why:
I predict that mostly gays are from western countries. There are still many kids who are growing without parents. If gays would have right to adopt kids, these kids growing in gay family can understand it as normal thing and and they can become to be gays. In mostly European countries more people die than born, so, growing amount of gays can have negative impact for country population in long term. But, it's only my conspiracy theory.
In other case, kids who are growing in gay family can be discriminated by other kids in school.