Why are people threatened by "redefining marriage"?

I wrote this a while ago, and forgot.  I think I meant to proof read it.  I've (obviously) posted it now.

Will and I went to an evangelical christian wedding on Saturday, and I finally heard for the first time the rationale behind the opposition for "redefining" marriage.  I think it's important in any political debate to understand both sides, so I'm going to share my insight here.  Though admittedly I did not talk to or even go near the minister afterwards to double check I got this right.
  1. The basic assumption is that marriage is about producing stable homes for children.  While no one will say that lack of children should annul a marriage, at the same time we should be honest and realize that of course most marriages do either result in or from children and either way wind up with families that are bigger than couples.
  2. Almost everyone in society will agree that protecting children is important.  Divorce actually takes five years off the life expectancy of children, so preventing unnecessary divorces is a reasonable goal.
  3. Child-rearing is difficult for both parents, but the difficulties are asymmetric. It is still easier and more likely for the man to leave.  In most though of course not all cases, the man has more power and money and less attachment to the children than the woman.  Even if we assume all else is equal, I've heard women who left their children described as totally and inconceivably unnatural, whereas men in that situation are just thought of as jerks, or even just as victims of a failed marriage.  So the biggest / most probable risk to children is the father leaving the family.
  4. The evangelical pastor advised / mandated that women must be respectful, supportive, and deferential to their husbands.  A wise strategy for keeping someone happy if you are in a subordinate position– that is, if you are dependent on someone.  And that the man must feel that the woman (and the whole family) is a part of himself, that he is the head of the family like Jesus is the head of the church, and that he must be willing to entirely sacrifice himself for that family, give away his life (at least temporarily), as Jesus did for the church.  Again, in turning the sacrifices by father into a noble display of power, the church is in some ways supporting the wife in her bid to make the benefits of marriage outweigh the costs so the guy stays.  But the minister didn't put these reasons in, he quoted new testament and old testament scripture and said "that's what God says."
  5. So here the problem of "redefining marriage" becomes clear.  If marriage can be between two equals, evangelical pastors would have to admit that equal partnership is possible, just not probable in heterosexual child rearing.  That asymmetric marriage is not a part of a beautiful mystery or a divine edict, but rather a hack to cope with the unfairness of biology.  This might make it harder to convince some people (both women and men) to play along with the biblical edicts.
Obviously I think it would be better to support a wide diversity of relationships.  People who love and depend on each other need to be able to support each other, but the law makes this hard if you aren't legally married.  This problem extends beyond gay and childless marriage and into issues such as elderly siblings who live together or own property together.  Personally, I do think it may very well make sense to treat parents differently than non-parents, but I don't think it makes sense at all to treat gay couples differently than heterosexual non-parents like Will and I.

This is why I've always supported gay marriage, since the time of my own.  I couldn't see why any other couple who fell in love should be forced to give up their relationship just because they were from different countries.  And I could never see how other couples could in any way threaten my marriage.  In fact the marriage equality movement has made me more aware of my own rights and responsibilities as part of a married couple, so strengthened my marriage.  But after this weekend, I suspect that no one seriously thinks our marriage, a childless marriage, is the type that would be threatened.  I think the rationale is that gay marriage threatens the marriage of people who need faith-imposed dominance-subordinance relationships to get through the difficult years of having young children around.  Young children are what really completely change the majority of what marriage is about and home life is like. 

Well, anyway, I could be totally off base.  But as I was sitting in the service trying to decide whether to get up and walk out, I was wondering why I was more offended about what was being implied about gay marriage than what was being openly stated about female subjugation.  And then it struck me, that because of the relationships I'd seen get in trouble in those early years of child rearing, the strategy being suggested was honestly pragmatic & fairly simple to implement. Of course I certainly hope and trust that institutionalised sexism is not the best method we can think of for making families stable.  But previously the exclusion of gays (and "selfish hippies") seemed just purely arbitrary and hateful.  At least now I see the nature of the fear that motivates that hate.