There is no basic human right to have other people recognize your relationship just because you say so.
Historically how would you tell if someone was able to procreate beforehand?
And as you said historically it would be grounds for divorce afterward, which was on a practical level the only way to tell. There is ample evidence showing the connection between a couple procreating and marriage.
What magic science allows a baby to be made from 2 sperms?
I do believe that there is a basic human right to the pursuit of happiness as a basic human right to be treated equally the law. While government may infringe on those rights, it should always be required to show a compelling societal interest requiring that infringement to do so. This is about government, not people recognizing one's marriage. As long as you do not unlawfully discriminate, you are still free to not recognize the validity of a gay marriage or an interracial marriage or fat people or whomever you hate.
No menses, no baby. No testes, no baby. Neither of these conditions were ever grounds to prohibit marriage.
From two sperm, no. From an egg and a donor sperm, or from a sperm and a donor egg and surrogate womb, yes. Unless you propose denying these things to couples with fertility problems, I see no reason to not characterize this as procreation for gays. In any case, unless you propose barring infertile straights or penalizing those who marry but choose to not have children, I see no reason this applies specially to gay people.