We have a three-year-old Female English Cocker Spaniel that is aggressive with larger dogs, Rottweilers and German Shepherds in particular.
The last trainer we went to literally wanted our dog to respond to our thoughts with no other direction. Needless to say, this did not go well.
I swear the dog-training world is full of people more than a few kibble short of a full bag of dog food. I have been in the company of more of them then is fair for any human being not being paid a large sum while wearing a white coat. I’m not saying that in some string theory alternate universe there isn’t a reality where humans can think their thoughts directly into the brains of their dogs and unicorns but mine and that of my clients is a tad more mundane.
I know this character is a bit of an extreme but she’s not that far removed from those in the dog-training world that have “new scientific evidence” that we can, in a typical environment, train our dogs, other animals and even our children by being all positive all the time. Like the thought transmission methodology, it will only take the average dog owner so far.
I’m surprised my psychic colleague didn’t pick up on the irony that an English Cocker Spaniel focuses its dislike on two breeds of Germanic decent. Surely that is evidence enough to indicate that the core of the problem is that your dog is a reincarnation of a victim of the Luftwaffe’s Battle of Britain blitz in WW2 and requires treatment for posttraumatic stress disorder.
Whether it’s these sorts of extremes or the other where some brute can’t tell the difference between discipline and abuse, it has got to the point in the dog training world where dog owners can’t assume because the sign on the door says, “Dog Trainer” that the person on the inside is necessarily “home” and the principle of caveat emptor holds.
In our plane of existence, sometimes these things are due to early life experience. I’m not a big fan of these puppy socialization classes where they let puppies run amok. It doesn’t take much for a larger breed to smush a smaller and leave a lasting and very specific imprint. Dogs, particularly between 8 and 10 weeks of age that have been abused by people, have been known to have their skittishness and/or aggression triggered by people of the same gender, height, hat or sunglass wearing etc. I’ve seen breed specific aggression result as well.
Another possibility is we can unconsciously transmit some level of bias to our dog. I think the average person walking a puppy or a small dog that sees a German Shepherd or a Rottweiler coming might naturally worry, “Holy crap, a German Shepherd/Rottweiler is coming. It might eat my dog!”, and snug up on the leash and/or cross the road, or even pick the dog up. After a while a lot of dogs are going to connect the dots available and conclude that big dogs are trouble.
You can desensitize a dog with these characteristics, even turn them right around but you have to have access to an upside alternative to the source of the anxiety. Too bad there wasn’t a canine version of pubs or Oktoberfest. That would result in a more likely meeting the “minds” involved and free you from your psychic stress. Instead see if there is a local German Shepherd or Rottweiler club that will work with you.