The Democratic Party is following a policy of minimalist incrementalism. It's the Democratic equivalent of “What's the Matter with Kansas.” The Republicans promised religious conservatives everything and threatened them with Democrats if they did not turn out to keep them in power. But the Republicans never delivered on the promises that they made to the religious conservatives. Ultimately, the Republicans lost because their goal was so toxic to their base that they injected political toxin–the religious conservatives have been abandoning the Republicans in droves because the real goals of the Republican Party starved them out and left them withered on the vine.
The Democratic Party is doing the same thing with the GLBT community. We've been historically the most reliable constituency for the Democrats–better than 70% vote in each election and we turn out overwhelmingly (70-80%) for the Democrats. The Democrats feel that they can't afford to deliver on any promises to the GLBT community because if they do, we might become complacent and not turn out to vote, keeping them in power. The Democratic threat is that if we don't vote, the Republicans who actively hate us will take over. The problem that the Democrats are facing is that the GLBT community is different from most other parts of the coalition–when we come out, frequently we are coming out of our families and social support nets, also. The act of coming out is an act of acknowledging that we can survive without the social supports that sustained us in our childhood.
So now the Democrats are realizing that they will actually have to deliver on some of the promises that they made to us. In the big political chess game, that means potentially driving away some of the constituencies that are hostile to the GLBT community. In a very real way, we are threatening to break the Democratic Coalition because we are naturally allied with some other constituencies, but opposed to others. One of the best analogies of this is from the Steve Jackson Games game “Illuminati” which has alignments like “liberal/conservative” and “straight/weird”. The Democrats have cobbled together some constituencies in the Greater Democratic Coalition that are inherently inimical. The Party fears that if they deliver too much to the GLBT constituency, they will have passed a point where other constituencies with opposite alignments get upset and threaten to leave to be fed upon by the Republicans.