The issue is not whether Christ is present to sinners.  He is.  Thank God, as we are all sinners.  Rather, the issue is the meaning of his presence.  For that we go to the famous scene in John's gospel.  Jesus rebukes the adulterous woman's accusers and extends mercy to her.  Then he tells her to go -- AND SIN NO MORE!  There is no contradiction between his forgiveness and his command.  As with the woman, so with all of us.  I guess, come to think of it, that by commanding the woman to change her behavior and reform her life, mean old Jesus was a...<gasp>....rigorist.