A Question about Prop. 8

The passing of Proposition 8 in California a couple of weeks ago makes gay marriage unconstitutional in that state; protests have begun and it's likely that the short term local defeat will lead to a movement that will eventually provoke a reversal at the national level. From my perspective, it should be untenable for a country that prides itself on liberty and justice for all to continue to refuse the right to legal protection and benefits to people who want to ratify their partnerships; especially when so much of the rest of the democratic world has seen that offering civil partnership legislation to same-sex couples is not a travesty of 'traditional values', nor will it undermine heterosexual marriage, but is actually best seen as an extension of the principles outlined by the founders of the United States - when people recognise injustice, what they are supposed to do is end it, not enshrine it in law.

Meantime, the opposing factions in this culture war don't talk to each other very much, partly I suppose because they are afraid, partly because they don't know each other (or they don't think they know each other). One side sees the GLBT community as demons out to destroy family life; the other sees religious fundamentalists as their oppressors, out to take away their very right to a family life.

So the question I want to ask is: what exactly do the proponents of Proposition 8 think there is to be gained from preventing loving couples having the right to share their tax burden, visit each other in hospital, and live in the same country? It's a serious question; and I have genuinely never quite understood the reasons offered by those opposed to gay marriage. I have some more detailed thoughts on this, and hope we can have a dialogue here about this; I'd be grateful if any readers would like to kickstart it by posting their responses to this question: How does gay marriage negatively affect anyone who is not gay?