In recent pop-culture history, as Thorin Klosowski noted earlier today, there's seldom been a construct as simultaneously embraced and rejected as hipsterdom, and this comic is an excellent example of the phenomenon: While it pokes fun at hipsters, it's at the same time true hipster humor, essentially self-referential. From the stiff, clip-art style illustration (clearly a nod to David Rees' "Get Your War On," which mocked the war on terrorism using a recurring cycle of the same illustrations) to the wry, low-key punchlines, "Hipster Hitler" is too accurate a portrayal of what hipsters think is funny to come from anyone but hipsters.
Being ironic, as usual.