1. That's not a reason to deny it because the couple is the same sex.
2. Apparently American isn't a western civilization now. And I believe they had to define it legally in the last few decades. Before it wasn't necessary.
3. This could be an argument for more immigrants as well since they're all hard working while native born are lazy, selfish brats. Gay people can adopt and raise children, just being born doesn't mean the child will grow up to become a lawyer.
4. See #2. It wasn't necessary because everyone was homophobic assholes.
5. A) you don't get to decide that gay people can have relationships and B) this is a pretty bad reason to not support gay marriage. Who cares what it's called?
6. They've revised that book several times.
7. Sure to polygamy and sterile relatives, though with some added stuff (both relatives are sterile and this is documented and contracts in case they get divorced/separated to determine who gets what property, child support, etc). Animals can't give consent at all and child/adult marriage is unfortunately a thing.