I was wrong.
That honor would belong to groups of gay men, humans who are neither capable of pregnancy nor who regularly impregnate women, who demonstrate a willingness to throw the reproductive rights of women under the bus if in doing so, they can advance their own gay rights agenda.
This phenomenon is classic kyriarchy, or "the human tendency for everyone trying to take the role of lord/master within a pyramid." In short, individuals are capable of being both oppressor and oppressed since privilege and power accrues to individuals on the basis of multiple identities such as sex, gender, race, sexual orientation, able-bodied-ness and religion.
Thus, it is the oppressed equality-seeking gay male who nonetheless possesses the male privilege of believing abortion rights to be a negotiable bargaining chip for obtaining gay rights.
Observe, Stephen Miller writing in the disproportionately-male-heavy Independent Gay Forum:
"...[G]oing back to Gerson's initial point about abortion, many leading gay political groups still maintain a pro-abortion-on-demand litmus test for candidates they'll endorse, including the Gay and Lesbian Victory Fund. This effectively eliminates many Republican gays—and gay-supportive but pro-life Republicans (and a few Democrats)—from ever being backed by these officially nonpartisan LGBT groups."
That is, that many LGBT rights groups oppose anti-choice candidates ensures that anti-choice, pro-gay candidates are not supported by the LGBT community which, in turn, could harm the overall LGBT rights movement. Wow. One sort of gets the impression that some gay men would sign the anti-abortion, anti-gay Manhattan Declaration if all that anti-gay stuff was omitted.
Oh, to be a gay man whose only axis of oppression is his homosexuality. Or, as commenter Bobby notes:
"Gay organizations need to focus on gay rights and nothing else."
Right, because didn't ya'll hear that racism and sexism are totally over, thus eliminating the need for social justice alliances?!
But seriously, I do wonder if Bobby is under the impression that no gay people are women or people of color or disabled or immigrants. For, only in a world in which all gay people were white, able-bodied gay dude citizens would all gay people be totes okay with the organizations supposedly representing them only focusing "on gay rights and nothing else." Only in that world would all gay people have no cognitive dissonance about supporting pro-gay candidates who were anti-choice (or anti-immigrant, or any other anti-).
Only in that world would gay rights be the only rights that mattered.
Most people in the world possess at least one marginalized identity. Many people are marginalized on the basis of multiple identities. Because of that, many gay people are not entirely comfortable choosing a candidate based solely on his or her (but probably his) position on gay rights, as that sometimes entails choosing a candidate who is anti- something else that is very important to those who do not have the privilege of "only" being oppressed on the basis of homosexuality.
So welcome, ladies and gentleman, to a large reason as to why the white male-dominated LGBT community does not have the support of some minority communities, as evidenced by Prop 8. Privileging their own oppression as gays, some gays support the oppression of other groups while nonetheless demanding the full-fledged support of the groups whose rights they are so ready and willing to sell out.
Although US statistics are lacking, the white gay male population constitutes perhaps 1% of the population. Perhaps they think they can win this "gay rights" battle on their own, selfishly demanding everyone else's support for their Most Important Civil Rights Cause Ever while offering no support in return. Lucky for them, many allies to the transgender, bisexual, lesbian, oh and gay community aren't so single-minded in their social justice activities.