Rebbe Nachman of Breslov wrote this:

Know this: You should judge every person by his merits.  Even someone who seems to be completely wicked, you must search and find that little speck of good, for in that place, he is not wicked.  By this you will raise him up, and help him return to G-d.  And you must also do this for yourself, finding your own good points, one after the other, and raising yourself up.  This is how melodies are made, note after note.