All right, I have a bit more vim this morning, so here goes:
Almost all of the humor in Portlandia derives from making fun of people who are utterly convinced they are superior to others, often for reasons that seem absurd to outsiders. In making fun of them, however, Armisen and Brownstein are acting just like their targets: they are as persuaded of their rightness and the wrongness of others as those feminist bookstore owners or the bike messenger. The humor has everything to do with "us" (Armisen, Brownstein, and the viewers) ridiculing a series of "thems." Maybe A. and B. are aware of the irony that they are engaging in the same behavior as those they deride, and I'm just missing it; but, even if they are, the humor remains cheap and mean-spirited. I may find annoying most of the "thems" on the show, but I sure as hell don't like "us," either.