And here is where the most fundamental difference between the Democrats and the Republicans might come into play. Ideology is ideology, but this is attached to the defense spending authorization thinger. If this doesn't get passed, then my understanding is that the military is completely unfunded and risks shutting down. So we have the Republicans refusing to pay for the military at all if the repeal's in there, and the Democrats facing the choice of either pulling DADT from the bill, or letting a major and essential part of the government grind to a halt.
And ultimately, I don't think the Democrats are willing to shut down the government to bully people into capitulating, because that has massive negative consequences for everybody. And it doesn't work in the other direction, because Republicans are psychotic enough to see government shutdown as a bonus. This is why the Democrats work with Republican majorities to try to make the best of a bad situation, while Republicans filibuster everything that risks coming in front of a Democratic majority. This is why the Democrats are seen as weak. Because as a group, they don't want to let millions of other people suffer so they can make ideological points for the cameras, and the Republicans are not only willing, but eager to do so.
It'd be nice to see the Democrats take that angle in the media. The Republican party is so afraid of the gays that already serve doing so openly, that they'd rather not have a military than have one with open gays in it. But then, while I'm not one of the people who'd be directly hurt by the delay, I am aware they exist and am not a sociopath, so it's hard to support the hard line.