Trouble is that a high number of dogs will bark, especially through a closed door, but post folks cannot distinguish between one that will bite and one that will not.
(We had a Dobermann who was as daft as a brush, but will bounce off the gate barking. I do remember a mum walking past who was startled when she did this, until her 5 year old said "shut up Jenny" and she turned and came back to me (I was digging the garden). The children would often come in my back gate to play with her, so the little one was quite used to her). However, when a man tried to grab a neighbour's boy, she left my side and raced to get between them snarling. I do not know what she would have done if he had not let go and run off.