Dogs need to know that their owner will not put them in harms way so if this happens on a walk, cross the street, or turn in the opposite direction of the person/dog
Teach a leave it and a heel command to one hundred percent and use this as you walk at a distance from someone.
Don't try to have the person offer a treat by hand, they can however drop a treat on the ground and they should totally ignore the dog.
Strangers should not be allowed to just approach him or they may get bit.
Do some behavior adjustment training with the dog and use friends and relatives to be the strangers.
If the dog's temperament is fear/ anxious, it is likely the dog will never trust strangers because this type of dog needs to see consistency in its life. Strangers do not show consistency.
Zac George -loading the clicker
Clicker training/positive method training/ print off
Behavior Adjustment Training
use a variety of items for training leave it so the dog knows it pertains to everything in its sight. Include using a remote control car for moving items
clicker leave it https://www.youtube.com/watch?v=zNAOe1djDyc