To the question: "How does legalizing marriage means they can get a kids?"
Simple. Since gay marriage is now legal, it now has to be recognized in schools. Now little Bobby, whose parents are divorced, has to have the same acceptantance as Susie, who has two mommies who turn into rabid vampires who eat babies as all lesbians do at night and have the agenda of turning kids gay, since obviously they have to do that themselves since homosexuality is a choice and they can't have kids themselves.
And obviously no one is ever born gay, because the parents would have been born gay from two straight people.
So, by being "legitimate" parents (i.e., married) they send the message that being gay is okay, so they can indoctrinate more kids to be gay.
At least, that's what this person thinks.
Honestly, when/if I do have children, I would love if one of their best friends had two mommies (or daddies) because one of the reasons I want to have children is to have more tolerant people on earth. My best friend in elementary school just "[didn't] have" a dad (her mom told me this after I asked about him) and my dad let her stay at my house even more after that. So tolerance and understanding for special situations helps kids, rather than shunning them and filling them with impotent rage so that they become gangbangers and kill you when they're an adult.
Or otherwise become angry and hurt society.