Yes your quite right, your dog could have lost its life. From what you say the lady did not say her dog was predatory aggressive, your dog was the predator and the other dog reacted, the ladys dog had no interest in your dog, it did have interest in its own privacy & space.

Dogs don't say hello and even if they did there is no reason why another dog should say hello back if it's not receptive to having another dog interupt what's it's enjoying doing. The fact is your pup made an unwelcome nuisance of himself to one of his own species, the other dog reacted in canine language and in its own individual way.

Owners have two choices, they can ask the other owner if their dog is ok with strange dog running up to it or an owner can impose their dog on another dog and its other owner whether they like it or not, which is what you did, in other words some people think if dogs don't welcome interuptions then it should be compulsory to impose an interuption on the other dog. They are dogs and your dog could have been maimed, killed or badly bitten by another dog which was quite happy doing its own thing, it's never wise to let a dog run up to one strange dog, its more risky if its a pack (two dogs in this case).

So, please accept responsibility for the events, there is nothing in law to say that a dog must accept another dog imposing on it and nothing in your post suggests the other dog was predatory aggressive, which is a different thing entirley.