The most deliciously scabrous skit on the mid-nineties HBO comedy series “Mr. Show” was “The Dewey Awards,” which skewered the sanctimonious trend of rewarding A-list Hollywood actors for their “brave” portrayals of the autistic, the mentally retarded, and other less fortunate types. Those rankled by the sight of Dustin Hoffman and Tom Hanks playing these parts, rather than real-life challenged actors, could gasp in private delight at this long-delayed