Even if it were somehow tangibly demonstrated that gay marriage would have a negative impact on society, it's difficult to imagine that it could be more than a drop in the bucket compared to the Republicans' dramatic acceleration of our rush toward fiscal insolvency. Based on the social programs we currently have in place, the government's own auditors predict that the federal budget will balloon to 60% of the country's gross domestic product by 2080 - with more than half of that going toward interest payments.
Despite seven years of extreme fiscal irresponsibility (not to mention the various side effects of our "war on terror"), the religious right remains strongly supportive of their man in the White House and no less fixated on the 'evil gays' who are supposedly undermining our society. That's not to say that a balanced budget is the sole hallmark of good governance, but the latter seldom exists where there is no genuine commitment to achieving the former.
We must not let our rulers load us with perpetual debt. We must make our election between economy and liberty or profusion and servitude. If we run into such debt, as that we must be taxed in our meat and in our drink, in our necessaries and our comforts, in our labors and our amusements, for our calling and our creeds... [we will] have no time to think, no means of calling our miss-managers to account but be glad to obtain subsistence by hiring ourselves to rivet their chains on the necks of our fellow-sufferers...
And this is the tendency of all human governments. A departure from principle in one instance becomes a precedent for [another]... till the bulk of society is reduced to be mere automatons of misery... And the fore-horse of this frightful team is public debt. Taxation follows that, and in its train wretchedness and oppression.
-Thomas Jefferson, Letter to Samuel Kercheval, July 12, 1816