In my lifetime (and I am now astonishingly old) I've witnessed dramatic declines in social and institutional biases against women, racial minorities, and gay people. When I applied to law school in 1971, sex discrimination in higher education was still legal and relatively respectable (Title IX, the federal equal education law, was enacted in '72), courts were still arguing about the application of landmark civil rights laws (see, Griggs v Duke Power Co.) and laws prohibiting discrimination against gay people (much less allowing gay marriage) were practically inconceivable. But while many biases have changed in the last half century, one remains the same: the bias against atheists.
A majority of Americans consider belief in God essential to morality, the Pew Forum confirmed in 2007; and Pew recently found that most Americans do not want their family members marrying atheists. (Note to Brit Hume: I doubt that most Americans would exhibit comparable hostility toward Christians.) The new Pew Research Center report on increased optimism among African Americans notes that while "interracial marriage is now widely accepted by Americans of all racial groups ... there is one new spouse that most Americans would have trouble accepting into their families: someone who does not believe in God." Resistance among people affiliated with a religion to intermarriage with atheists may be stronger than their resistance to gay marriage: seven in ten religious people surveyed by Pew would oppose or resist intermarriage with an atheist. And while comparably high percentages of the most regular churchgoers oppose gay marriage, opposition declines significantly among the less devout.
Given our general progress toward gay rights in recent years (notwithstanding a few reversals in the fight for equal marriage), you might expect gay people to encounter less overt hostility than atheists. But it's worth noting that 25 or 30 years ago, when homophobia was quite strong and socially acceptable, antipathy toward atheism was, in some instances, even stronger. In their 1983 book, Dimensions of Tolerance: What Americans Believe About Civil Liberties, Herbert McCloskey and Alida Brill reported that 71% of people surveyed believed that atheists "who preached against God and religion" should not be permitted to speak in civic auditoriums, as opposed to 59% of survey respondents who believed that gay liberation groups should not be allowed to use public halls to advocate for gay rights.
I don't mean to set up any grievance competitions between historically maligned groups, much less suggest that being an atheist in America is harder than being gay. In general, closeting your lack of faith is probably easier and a lot less stressful than closeting your sexuality. Besides, no one can accuse the "new atheists" of being closeted, or otherwise shy in expressing their disdain for religion, as well as their own disbelief; and they don't lack bully pulpits, which were harder to find a decade ago. (In the mid 1990s, The Atlantic killed an assigned article I wrote in defense of atheism; it was published in 1996 by The New Republic, entitled The Last Taboo). Non-celebrity atheists and agnostics have also begun organizing politically through organizations like the Secular Coalition for America (which I advise).
So I'm not ignoring the beginnings of what some consider an atheist liberation movement (although American atheists are not exactly oppressed). And I'm not complaining: I don't care if religious people consider me amoral because I lack their beliefs in God. I do, however, care deeply about efforts to turn religious beliefs into law, and those efforts benefit greatly from the conviction that individually and collectively, we cannot be good without God.
Persistent hostility toward atheism may not be a source of educational or employment discrimination for individual atheists (although it does engender significant discrimination in the military), but hostility toward atheism is a threat to freedoms of conscience and religion that all of us share. It's an often overlooked irony that atheists who regard all religions with equal disrespect, favoring no one faith over another, are sometimes the most reliable defenders of equal religious rights. But you shouldn't have to be irreligious to consider religious liberty transcendent.