Similarly, renters have the right to get a mortgage subsidy by buying a home. They may not prefer it, but they have the right to do it. Thus, the mortgage subidy discriminates against people who prefer rentals.

Should we therefore eliminate mortgage subsidies (or any number of other laws which favor one preference over another) subsidies based on the same logic?

The right in question is not the generic right to marry someone, but rather to marry the person you want to marry (if that person will have you). And it's pretty settled at this point, since the definitive ruling was over 40 years ago; Loving v. Virginia struck down "everyone is equally free to marry someone of the same race as themselves" as discriminatory, and this case is now simply following the logic to strike down "everyone is equally free to marry someone of the opposite sex".

As to your mortgage examples: marriage is and has long been held in US law to be a fundamental right. Renting a house, meanwhile, is not and has not been held to be such a fundamental right. And specifically in the case of laws which subsidize buying but not renting, such "discrimination" is allowable so long as it serves a compelling government interest. Proposition 8 was found not to serve any such interest; its sole purpose was to make law out of the religious beliefs of a particular group, and this is not something government legitimately can or should be doing.

If increased probability of positive effects is sufficient rational basis for government acts, then it is very easy to come up with a rational basis for supporting straight marriage (but not gay marriage) based on positive externalities generated for children (e.g., straight couples are more likely to have children than gay couples).

I came up with a rational basis given only a few minutes of thought. I'm now a bit surprised that the judge couldn't come up with such an obvious rationale. It's almost a if he was making a political decision rather than a legal one.

The argument presented to the judge was exactly the basis you've pointed out: that the sole purpose of marriage is to encourage procreation and to provide a stable environment in which to raise children.

If you'd actually read the ruling, you'd know that the evidence presented for this was flimsy at best; it was not demonstrated that heterosexual parents do a better job of raising children than homosexual parents, and it was freely admitted that marriage licenses are granted to heterosexual couples who are unable or unwilling to procreate. Thus the argument was rejected as legally unproven, and the ban on homosexual marriage was found to have no legally acceptable basis.

(and again the parallels with racial bans are striking: it was argued, once upon a time, that interracial couples would produce inferior children and that the government thus had an interest in preventing such couples from marrying. Such arguments were similarly unproven, and ultimately unprovable)

The evidence doesn't need to be anything other than flimsy to constitute a rational basis. Courts are not supposed to evaluate the facts at all, but should merely determine if there is any rational basis for the law given the most generous possible interpretation of the facts.

"[A] legislative choice is not subject to courtroom factfinding and may be based on rational speculation unsupported by evidence or empirical data."

http://www.law.cornell.edu/supct/html/92-351.ZO.html

http://volokh.com/2010/08/05/more-on-whether-the-facts-matte...

If the job of the courts was factfinding, a huge number of laws would be eliminated. For example, could you prove in court that the Bush tax cuts, obamacare, minimum wage laws, gun control laws, or any other law are beneficial? I rather doubt it.

As long as one can imagine a scenario in which health insurance is related to health, Obamacare passes the rational basis test. And as long as one can imagine a scenario in which straight couples make better parents than gay couples (even if only in a probabilistic manner, i.e. 95% of straight couples are fertile compared to 0% of gay couples), then Prop 8 also has a rational basis.

The ruling correctly states that, due to the nature of Proposition 8, strict scrutiny would normally be the appropriate level of review. It concludes, however, that strict scrutiny isn't needed because Proposition 8 doesn't even survive rational basis review, and goes through each proposed rationale:

1. Heterosexual marriage is traditional. As Judge Walker points out, this fails as a rational basis since "the state must have an interest apart from the fact of the tradition itself."

2. Overturning Proposition 8 would phase in a social change. But California has already, in the past, permitted same-sex marriages, so: "The evidence shows that allowing same-sex couples to marry will be simple for California to implement because it has already done so; no change need be phased in."

3. Opposite-sex parenting is better than same-sex parenting. This fails because California already permits same-sex couples to adopt and raise children, and because "Proposition 8 does not affect who can or should become a parent under California law."

4. Proposition 8 protects the free-speech rights of those who oppose same-sex marriage and want to teach their children to be opposed to it. But Proposition 8 is only concerned with permitting or forbidding certain marriages, not with allowing speech or education concerning marriage: "as a matter of law, Proposition 8 does not affect the rights of those opposed to homosexuality or to marriage for couples of the same sex."

5. Homosexual and heterosexual relationships are different, and must be classified differently. This fails because "same-sex and opposite-sex unions are, for all purposes relevant to California law, exactly the same."

There's also an alleged "catch-all" interest. I'll just quote that one in full:

Finally, proponents assert that Proposition 8 advances “[a]ny other conceivable legitimate interests identified by the parties, amici, or the court at any stage of the proceedings.” Doc #605 at 15. But proponents, amici and the court, despite ample opportunity and a full trial, have failed to identify any rational basis Proposition 8 could conceivably advance.

The important thing to remember in reading the above is that rational-basis review, while not particularly demanding, is not the same as no review. "I say there's a rational basis, therefore there is" doesn't hold up in court; you'll have to make an argument and it will have to actually make sense. The arguments advanced for a rational basis for Proposition 8 failed -- they either did not assert a valid basis for legislation or were contradicted by other established law or by Proposition 8 itself.