"Dogs are unpredictable."
Motorists say the exact same thing about cyclists... "those cyclists swerve, they don't signal, they don't look back, they should stay to the right." All comments made by motorists regarding cyclists...
Substitute dog in above quotes, and it is exactly what you folks are saying.
Sorry... any overtaking traffic has the responsibility to ensure that it is safe to pass, before such an attempt is made. This is written into every traffic law and even maritime law.
If the walker and dog in front of you will not yield to your passing signals, I suggest you get off the bike, walk on the side away from the dog, and proceed past this obstacle.
Consider the case of a motorist coming up to a peloton on a roadway. The driver must wait for the way to clear, before proceeding.