The guy judged the old man just because of his eye.
Do you think it's right to hurt someone you love? In my opinion, it's not right. In The Tell Tale Heart, the guy decided to kill the old man, even though he loved him.
The cops came to the old mans door because of the neighbors reporting sounds. The guy brought the cops into the house and asked if they would like some tea. The guy heard noises, that he thought everyone else could hear, but only he heard. This lead him to go. Crazy and give himself away.
In conclusion, the point the author was trying to get across was you should not hurt someone, just because of how they look. The guy hurt the old man because he had an eye that looked like a vulture.