Despite a long history of ostracism, the gay rights movement today has some advantages denied to pro-life advocates. Higher education, entertainment and advertising tend to be gay friendly in a way that they cannot be considered pro-life friendly.
But much of the progress for gay rights has been parallel to the pro-life cause. The strategy of "coming out" has personalized this debate as surely as the sonogram. A 2009 CNN poll found that 49 percent of Americans report having a family member or close friend who is gay -- up 17 points from 1994. A human face always makes harsh judgment more difficult.
Also similar to the pro-life movement, many gay rights advocates have shifted their political argument. The activism of the 1970s was often motivated by sexual liberationism -- a revolutionary rejection of sexual morality and the idea of respectability. But a generation of thoughtful gay rights advocates, exemplified by Jonathan Rauch of the National Journal, has made the argument for joining traditional institutions instead of smashing them. More radical activists have criticized this approach as assimilationist and bourgeois. But only bourgeois arguments triumph in America. And many have found this more conservative argument for gay rights -- encouraging homosexual commitment through traditional institutions -- less threatening than moral anarchism.
It remains possible that the gay rights movement could provoke a backlash. If the Supreme Court were to strike down restrictions on gay marriage nationally, one could expect a Roe-like reaction in parts of the country. If the advance of homosexual rights were broadly used to undermine the tax status and funding of churches and charities that hold to a different moral standard, resentment and resistance would follow.
But so far the gay rights movement has succeeded for many of the same reasons that the pro-life movement (to a lesser extent) has succeeded. Both have taken sometimes abstract, theoretical arguments and humanized them. Both have moved away from extreme-sounding moralism (or anti-moralism) and placed their cause in the context of civil rights progress. Whatever your view on the application of these arguments, this is the way social movements advance in America.