That was actually a line from the dialogue of a Woody Allen film.  In context, the dialogue goes:

DORRIE   Hey, that's so pretty. A pigeon! 
SANDY    Geez...no, it's not pretty at all. They're...they're...they're rats with wings.
DORRIE   They're wonderful. No! It's probably a good omen. It'll bring us good luck.

Amazingly, the �rats with wings� label stuck, the �wonderful.....good omen� was swept aside!  Pest control companies and pigeons haters pounced on the unflattering description for their own purposes and used so often it is beginning to be accepted as accurate!  Which it certainly isn�t!

The Reality

They do not carry any more diseases than any other birds , few of the diseases that they carry are transmittable to humans and even those are very rarely transmitted.  This is what the British Government vets said about the health risk the Trafalgar Square pigeons posed to the public:

"My Lords, advice from our veterinary team states that although diseases are carried by birds, those diseases are likely to be conveyed to human beings only when they are in prolonged contact with pigeons in enclosed spaces in the presence of dust from feathers or guano, and when eating food contaminated by pigeon droppings. None of those conditions applies in Trafalgar Square"

Pigeons are extraordinary birds.

Can it be a coincidence that of all the birds in existence  it is the pigeon/dove that has been the chosen symbol of hope, love, purity, the Holy Spirit and also revered in Islam as the friend of the Prophet?