Jim: The trouble with “the decoupling of benefits associated with marriage from marriage itself except where those benefits are fundamental to the purpose of marriage (e.g., related to children and reproduction)” is that the child-rearing benefits of marriage are exactly what a lot of gay couples want — that is, they want to be parents (via adoption, artificial insemination, etc.), and they want to be treated as such. The mothers of married homosexuals — who are unlikely to be any less inclined than the mothers of married heterosexuals to ask “When am I going to be a grandmother?” — are likely to be a rather powerful force in preserving the traditional link between marriage and child-rearing.
The evidence that gay parenthood is harmful to children is rather weak — and it’s incontrovertibly better for a child’s well-being to have two parents than it is to have one. In the many jurisdictions where its legal for gays to adopt but not legal for them to marry, the link between marriage and child-rearing really is being stepped on. The social norm that makes marriage a prerequisite for parenthood urgently needs bolstering, and gay marriage may well be a boon on that front.
None of this should be taken as a defense of the California Supreme Court’s ruling; I’m still wading through the decision and its precedents, but so far I’m rather unimpressed.