Why does the author refer to Dimmesdale as a hypocrite even though Dimmesdale has confessed to being the worst of sinners?

In Chapter XX of "The Scarlet Letter," Hawthorne remarks, "No man, for any considerable period, can wear one face to himself, and another to the multitude, without finally getting bewildered as to which may be the true." Dimmesdale wears these two faces:  He returns from the forest encounter with Hester "transformed" as Hawthorne writes.  Dimmesdale has three urges to rebel against his false nature by insulting or lying to townspeople; he is tempted to sin. When he returns to his house, he sees the Election Sermon.  It is though another man has written this sermon as he now has more knowledge, a "bitter knowledge," the knowledge that he has been deluding himself. 

In the words of Emily Dickinson, when Dimmesdale does tell the truth he "tells it slant" not because the people will not understand, but because he has not the integrity to confess his sin as adultery; he is too weak to defend Hester and can only stand on the scaffold in the cover of night.  He feigns that his illness is only a physical illness, and he misleads Hester into believing that he will leave America with her, even deluding himself into this belief knowing he cannot bring himself to escape. He continues to wear "two faces" and is, therefore, a hypocrite.