Richard Ballantine is a Septic, and I have heard that some people in that country feel the need to keep a savage dog, especially in isolated rural areas, to repel intruders.
If I remember correctly, in a part of this advice not quoted above, he encourages the reader to remember that an adult human is a fairly formidable animal so that one should not be overcome by fear, but radiate aggression and give out the impression that any dog who tackles this human will regret it for the rest of its life (which may not be long). Equipping a cyclist with the knowledge of how to tackle a dog, and the self belief to do so vigorously, is a good way to help him/her give out the body language which can deter a vicious dog. Its often said that animals can sense fear, so this advice may well help one to stay unbitten without harm to the bloody dog.
I wonder if anyone, cyclist or not, has ever used Ballantine's attack stategy. I would doubt it.
I've sometimes had run-ins with dogs which chase bikes. I find going on the attack sometimes is the best tactic. I should add that so far this has only amounted to a charge with warcry.