Attractive people are significantly more kind, more intelligent, more honest, more sincere, less spiteful, less cruel, and less antisocial than unattractive people. You absolutely can and should judge a book by its cover. Anyone saying otherwise is most likely; ugly, attempting to deceive or harm you, or gain something at your loss for personal gain.
This is most apparent with overweight, obese, and tattooed individuals. There has never in all of history been a good fat or tattooed person. They are always lazy, petty, selfish, and dishonest. The church was correct in identifying gluttony as a deadly sin. Fat people should be shunned and punished for their wickedness. It's not like it happened by accident or suddenly without warning. The only way to get fat is to consistently act with immorality and evil in your heart.