Obama did not call Pennsylvanians bitter.  He suggested that it is not surprising that a certain subset of Pennsyvanians are bitter that their jobs have all gone away-- a statement that is completely true.  If Clinton made such a comment she would not have to worry about being forced out of the race.

Also, if you think the media is so biased against Clinton in the primary, what makes you think things would be any different if she were to go up against the Republican media darling, John McCain?