The inevitability of Gay Marriage

Here is the "why":

A gay marriage backlash? Not likely

[...] Four factors often predict whether judicial decisions will generate backlash: public opinion, relative intensity of preference, geographical segmentation of opinion, and ease of circumvention/defiance.

Unsurprisingly, only rulings that contravene public opinion tend to generate backlash. In 2003, Americans opposed gay marriage by roughly 2 to 1. Today, supporters outnumber opponents by 5 or 10 percentage points. A ruling in favor of marriage equality would generate far less backlash today than previously. Still, the nation was divided nearly down the middle when the Brown and Roe cases were decided, yet both rulings generated massive political resistance.

Backlash is more likely when opponents of a ruling care more than supporters do. In 1954, Southern whites overwhelmingly disagreed with Brown, and 40% of them regarded civil rights as the nation's most pressing issue. Most Northern whites agreed with Brown, but only 5% of them deemed civil rights equally important. Similarly, by 2004, among the one-third of Americans who supported gay marriage, only 6% said the issue would influence their choice of political candidates. Among the two-thirds who opposed gay marriage, 34% deemed it a voting issue.

That large disparity in intensity of preference between the two sides of the issue no longer exists. Perhaps more important, even strong opponents are unlikely to find that a marriage equality ruling will directly affect their lives in the way that Brown and Roe affected opponents. In the 1950s, white Southerners committed to white supremacy thought that sending their children to school with African Americans was the end of the world. Opponents of abortion regard the procedure as murder.

Constitutionalizing gay marriage would have no analogous impact on the lives of opponents. Expanding marriage to include same-sex couples may alter the institution's meaning for religious conservatives who believe that God created marriage to propagate the species. But that effect is abstract and long-term. The immediate effect of a marriage equality ruling would be that the gay couple already living down the street would become eligible for a marriage license — and nothing would change in the daily lives of gay-marriage opponents. That is why strong initial support for a state constitutional amendment to overturn the Massachusetts court ruling rapidly dissipated once same-sex couples began to marry. [...]

That explains a lot. Succinctly. And in IMO, makes it inevitable.