Some dogs find being on lead very restricting. If they are of a nervous disposition they often feel that they must protect themselves and their owner from approaching danger. Since the dog is unable to get away or show the correct body language they quickly use the most appropriate behaviour, barking ....
Understanding this you can see why taking a dog into a confined space with their worst fear, other dogs, drives the dog into a barking frenzy which then puts the dog trainer in a position of having to manage a barking dog. Dogs bark very loudly which means that the other attendees are unable to hear and learn from the dog trainer.
This is a video of Samson.
Which one do you think is Samson's problem?
We believe that most dogs are reactive on lead because they either; Samson ....
Does not know that he is a dog and is frightened by approaching dogs
He is desperate to interact with other dogs and the adrenalin released causes barking or
He is responding to how his mum and dad is thinking and feeling
Wookie used to be grumpy around dogs especially if he is on lead nobody really knew why ...
Brenna was so scared that she couldn't protect her Dad that she would bark at other dogs to keep them away from her.