I hate to ascribe cynicism to a Press Secretary.

Recently, some poll or other concluded 55% of likely voters think the President is a socialist or can fairly be described as one.   Secretary Robert Gibbs' derision of the "professional left" is probably intended to create vocal response from liberals to show Obama is anything but a socialist.  I doubt this is really about anger at liberals for not giving this administration its due, but by offering that as the narrative, Gibbs has given the press a nice package, which will include this White House's accomplishments while implicitly arguing against the notion that Obama is too liberal.

Do liberal pundits like playing along while their emotional buttons are pushed?  By playing the game as though there were no game, they offer their tacit approval of just that.