As a woman, I don't appreciate when I am home alone and salespeople or campaign volunteers knock on my door and stand right at the door waiting for me to open it. Disturbing my peace aside, please understand how unsafe a woman or elderly person might feel opening the door to a stranger. The appropriate thing to do as a strange unexpected visitor is to knock and then take 10 steps back and wait from afar for someone to answer your knock, not to hover in the doorway.