Merits of this particular test itself aside for a moment, I think our small sampling here reflects the actual makeup of the show's fanbase - at least as far as the chat, the messageboard, and the in-person gatherings show.
It's sad that "urbane" has to mean liberal (or at least, not conservative) at this point in our country's history. Regardless of what you think about their politics, most of the mid-century conservative lights were thinkers. You could certainly hate all of William F. Buckley's ideas, but he came across, in truth, as *too* urbane.
Nowadays, the most sophisticated conservatives are either distrusted as effete wannabe liberals (Ross Douthat, George F. Will) by most conservative voters, or simply turn their brains off and pander (I'll give Dinesh D'Souza and Jonah Goldberg the benefit of the doubt here).
The monolithic nature of the Best Show's audience is further proof to me of the "everything is political" nature of a country that really isn't that ideological in its daily lives. We look for shortcuts to turn us on or off to particular media options.
It's clear from listening to Tom talk and tweet that he holds liberal social and economic views, but that shouldn't necessarily preclude a conservative from enjoying the show (and its musical and comedic aspects, in particular). Somehow, it seems to preclude their enjoyment, though.
Maybe they're just listening and not participating in the group aspects. But I don't really believe that.