If Stephen Colbert is going to pretend to be a conservative, perhaps he shouldn’t play along when a guest compares President Bush to a genocidal dictator like Adolf Hitler. On the March 13 edition of "The Colbert Report," the Comedy Central host had University of Missouri professor Dr. Donald Shield on to discuss the (media generated) controversy over the firing of eight U.S. Attorneys. Shields was appearing to tout a study claiming that federal prosecutors investigated Democrats over Republicans by a five-to-one margin. However, the discussion quickly degenerated into Nazi comparisons with Colbert happily joining in: Stephen Colbert ".The Republicans are in power so they're using the full force of the federal government to target the Democrats specifically to make sure they get all the corrupt ones out of there. I mean, that's government efficiency." Dr. Donald Shields: "Well, that's kind of the way Hitler started out in Nazi Germany, isn'