All gay people who accept themselves for who they are constrained to be "socially liberal" which means that they accept sexual behaviour outside the average.
There is no reason that they should be politically or economically liberal as well. The ideology of libertarianism, once the cornerstone of the Republican party, guarantees freedom from persecution on the basis of gender, orientation, race or religion. It is in fact the ideology on which the US was founded, and is a coherent and admirable framework.
For now, the Republican party does not run such a manifesto: rather, it adopts the ideology of moral authoritarianism that is a consequence of courting the votes of the Christian Right. Gay republicans typically don't accept this ideology of course, but if they vote republican they do have to live with the contradiction.
The Democrats have perennially vacillated on gay issues. They promise much and apparently deliver little (we should not forget that to their credit, and in contrast to the republicans, they have delivered anything at all): but they do so simply because the "gay vote" is actually not very important to their power base. If we are to force the Democrats to do something, we have to MAKE ourselves important (this applies to Gay Republicans too). Political acces does not equal political power!
Throughout it's history the gay "movement", if it can be described as a coherent whole (I would contend otherwise) has been driven by volunteers who are a self-selecting group of people with a strong drive for social improvement. They are natural Democrats. To their credit, they have empowered millions to live open and satisfying lives that are coherent about their sexuality. To what ought to be the shame of Gay Republicans, they have done no such thing. They ought to do better.
As a result of this, the gay "movement" has been unaware that there is a natural variation in its internal politics. It has experienced the natural tension between "liberationists" and "legitimationists" but because it did not recognize that gay people within "the" "movement" straddle a broad political spectrum, it was unable to reconcile these tensions within itself.
We need a new movement that understands itself better. There are green shoots, though: the Iowa marriage decision (made by Republicans and consistently with the ideology of liberty I describe above); the wholesale rejection of Sarah Palin and her corrupt moral authoritarianism.
I think we all win if LGBT rights were no longer a political issue to differentiate parties. I think all of us, Democrats, Republicans and Independents can help to advance that goal. I think we can all do better.
[Yes, I'm on the left :-)]