Doesn't really matter the breed, a dog who is "protective" is a bad thing (unless trained to be)... it means they see you as their possession. Ideally you want your dog to look to you to protect it.
I usually have good search skills.. there are some good articles on retraining this behavior. I can't find them, though this article below applies to humans as well as dogs.
First I would suggest a trainer.
However, you can work on this. Take the dog and a friend (if your son is old enough, not if a child) to an area with people. Enlist the people to stay back, not look at you or the dog, toss a tiny treat to him. Keep this up day after day, several times each trip, until seeing people no longer puts him in attack mode.
Next, have them come a little closer, toss the treat and say "Hi" without looking at you. Same process.
Next, have them stay at safe distance, face you and toss treat then go on.
Next, have them look at the dog and say "good dog", toss treat and go on.
Next, have them stand and talk to you, tossing a small treat when they arrive and as they leave.
For many dogs, this process can help stop the reactive behavior.
Other than in those very controlled, you dog needs a muzzle in public. Do not risk him hurting someone or being put down.
https://positively.com/dog-behavior/aggression/leash-aggression/
