I know but someone could argue that if you don't know if you're sterile, you might not actually be (so you might accidentally get pregnant or get someone pregnant), and if you don't want kids, you could still have an "accident" and not be able to get an abortion for some reason (it's fucked up but it could happen--especially given the direction this country seems to be taking). But if you have a hysterectomy due to cancer or whatever, you know that you won't be able to have kids "by accident" ever. And without your 'nads intact, you're on the same footing as a gay person. (I'm just arguing that some straight people know as well as gay people that they won't have children with the partner they'd like to marry.)

And, actually, there is plenty of people who believe that folks who don't want kids should not get married because marriage is for the chuldrin; I happen to be one of such "baby-hating freaks" myself but, technically, I could still have an oops, and this whole legal argument seems perched precariously on the probability of oopses, so I'm "safe" here. Except that I still think that basing marriage totally on breeding capacity is messed up when many married couples choose not to or can't have kids and when many others happily have kids outside of marriage. Again, there are people who know perfectly well that they can't have kids under any circumstances, regardless of the sex of the person they want to marry.

(But reproduction is the only argument the sneaky bastards could make without directly invoking religion.)