Protecting What? And How?
If they were honest, they would have said something Fred Phelpsian -- something that captured the essence of Ohio's campaign against gay couples, like "God hates your kind of love" or "Legal limits on love. Vote yes."
But the yard signs -- like the whole Ohio campaign and the entire presidential race -- probably weren't that honest. They likely didn't present their explicit prejudice quite so explicitly. They likely used the same generic, innocuous-seeming euphemism of "protecting marriage."
Is it possible that banning same sex marriage might shore up the institution of marriage? Sure, inasmuch as the possibility isn't analytically impossible the way a square circle is. But the claim is prima facie implausible; as has been noted by many people, it's just weird to think that two women getting married would have a deleterious impact on the marriage of a man and a woman down the street. My hunch is that the sheer vapidity of the 'protect marriage' slogan masks the absence of a real argument. As it stands, the slogan version presents the argument as a consequentialist exercise in instrumental reasoning: 'If we want x, we must do y.' As Mr. Clark suggests, though, the real rationale is deontological: '~y is bad.' The instrumentalist version relies on a causal link between y and the realization of x. Absent a causal mechanism, though, the argument obviously falls apart, and the religious right hasn't really presented one (or if they do, they resort to wildly over-reaching arguments about the debasing of the culture, in which case we could just as easily ban sexual content on TV to protect marriage. Put differently, the net cast by this line of thinking is so huge that it proves too much).
The rational reaction is that the instrumentalist slogan is a facade masking the true reason: '~y': gay marriage is bad. Of course, they can't do that politically, since it would open a can of worms and deflect the argument from the value of marriage to the legitimacy and validity of conservative Biblical reasoning. So they have to jawbone the public with a bogus and incomplete contention that same sex marriage would, through some unspecified and magical mechanism, destroy marriage.
With respect to Ohio, this dissimulation is two-fold: not only is it not clear how a ban of same sex marriage would protect marriage, but the amendment itself goes far beyond banning same sex marriage.
What is especially disturbing is that some of the major proponents of the ban were Christians. The lack of intellectual honesty evinced is stunning, and goes a way toward explaining why it is that many people so disdain the religious right.