I don't especially care that there's no liberal equivalent of CPAC in terms of media attention, but it's worth examining why. Coverage of the bizarro (liberal) CPAC would be all about how major Dem politicians needed to "distance themselves from the controversy" and about how "has the Left finally gone too far? (for the hundredth time)". Years of attempted nutpicking at Take Back America or Yearly Kos have produced none of this, because the liberal conferences aren't the bizarro versions of CPAC.
But they do love their CPAC. Because conservatives are awesome!