Not by themselves. Banners are inert, they have no ideals--the ideals they come to represent are determined only by those who wave them. It makes no sense to tie one's loyalty to a symbol, since that symbol can come over time to stand for everything it once opposed. The GOP is a long way from Lincoln, and the Democratic Party is on a trajectory well away from Jefferson and FDR. If we only defend the name and trappings of a party, regardless of who wields them, its ideals will be as vaporous and inconstant as ambitious opportunists see fit to make them; the party will shift under our feet until we find ourselves far from where we thought we'd dug in.
This is why I value criticism and public pressuring, even of Democrats. Ambitious opportunism is a required trait in any political leader. It is our insistence on and support of certain ideals that must provide the best opportunities for ambition. If we don't provide them, they will be sought elsewhere.
If I were looking to defend anything done by Democrats, no matter what the party plans for the next two years, I would simply point to the evils of the opposition and the necessity of keeping them out of office. This sort of tough-talking pragmatism convinces a great many people (it convinces me!). Well, apply it to the politicians. If you want them to stick to a set of ideals, the alternative must seem an evil one to them. If you define yourself as an enthusiastic supporter of the trappings alone, they'll graciously look elsewhere for someone to please.