Couples who wishes to have children the "normal" way. I don't see anything wrong with gay marriage, and I, at least tacitly (based on WA voting records), support it, but one of the tenets of marriage is procreation, and should be taught as the norm to children. That doesn't go to say teach gay marriage as sinful or an abomination, but that it cannot physically achieve a major foundation of marriage.
Same reason that sex-ed, woefully insufficient though it may be, should not teach anal sex, regardless of gender, as the norm.
Since we like to get all indignant about perceived slights and misinterpretations, this is not in any way meant to belittle gays.
No Klingsor, not the intent at all. Perhaps you don't preach hetero marriage as "normal," which would insinuate anything outside of it is abnormal, but, again, from the child bearing perspective, it should be preached as the way to do it.