The left has no particular place it wants to go. And, to rehash an old quip, if you have no destination, any direction can seem as good as any other. The left careens from this oppressed group or crisis moment to that one, from one magical or morally pristine constituency or source of political agency (youth/students; undocumented immigrants; the Iraqi labor movement; the Zapatistas; the urban “precariat”; green whatever; the black/Latino/LGBT “community”; the grassroots, the netroots, and the blogosphere; this season’s worthless Democrat; Occupy; a “Trotskyist” software engineer elected to the Seattle City Council) to another. It lacks focus and stability; its métier is bearing witness, demonstrating solidarity, and the event or the gesture. Its reflex is to “send messages” to those in power, to make statements, and to stand with or for the oppressed.
This is in part — in the context of politics in the US — because those on the left want what the rich/powerful don’t want and yet the left must at some level appeal to the rich/powerful in order to maintain their own power.
See also Murc’s law and The purpose of a system is what it does.