List_House -  Wyatt probably just needs some more exposure to dogs, people and different places.  I would not make a big deal of the fear.  Pups go through several fear stages and he may actually be in one right now.  I would just keep taking him to a variety of places and play with him, give him treats and make it fun.  He will eventually come out of his shell.  Just don't baby him or fuss at him. Treat him like everything is perfectly normal.

Well you kind of threw me off with this,

"The other night he was in the yard with my husband. Neighbors walked by with their 1-year old GSP (male, intact).  Bo and the other dog sniffed, then Bo snarled, jumped on him, and took him down! (I wasn't there).  My husband was beyond embarrassed."
 

Rememer dogs don't recognize nor understand property lines.  He was in his mind still pretty much on his home turf, and he had your husband to protect.  Remember one of the POSITIVE traits of the bree is that they are protective.

I'm not "anti dog park", I just don't like having my dogs put into situations where they are exposed to dogs who may or may not be vaccinated, and who may or may not be out of control, and may or may not be aggressive where I cannot do something about it.  Obviously dog parks fall into that category.

If I lived in a city and had no where else to go with my dogs I might do the same thing.

But that's a very large part of why I will never live in the city if I can possibly avoid it.

They were never breed to be man aggressive.

There's a big difference in "man aggressive" and protective. All of dog behavior cannot be easily piigeon holed into one or two slots like, aggressive/dominant/submissive/subservient. There's also a difference between aggressive and vicious. If a dog isn't protective of my home, property, and family I have no use for them.

Rocky is PROTECTIVE!!  No problem in open fields, in dog parks, backyard with the neighbor kids throwing ball to him. His protective gaurdy times are when he is on leash with me. So I just walk him on leash and hope for many distractions so I can correct him with the "leave it command" when his forehead un -wrinkles I give him much verbal praise. Also Rocky gets in a jumble with an ambulatory delivery person going to anyones house. UPS Guy, Our mail person, Fed Ex. they are all on Rocky's list. He agressively barks at them. So at this point, I would never trust Rocky not to bite a delivery person or a stranger coming up to pet him if we are on a leash walk.  The front door is the gaurdy barky door and our garage door is Rocky's happy door who he greets tail wagging  family and friends. In Rocky's mind bad people enter the front door and good people enter our house thur the garage door. So I always tell my friends to come to my garage happy door  So you can see Rocky and I have lots to work on!! We are deeply in the social GSP training Club along with Bxr-Linda's Bo, Bean girl and now I see after reading some of this thread. Ruby girl can join as the newest memberWelcome Ruby!!  PS Rocky did pass his Canine Good citizen test the first time as there were no Mail men or front doors on this test

Linda ... like I said, this situation sounds exactly like what happened between our Bo and his buddy Hershey. Just keep an eye on it. These guys tend to sound pretty fierce even when the situation is under control.

My girls are the protectors in the family right now.  Ringo is still figuring all that out and will follow whatever Belle does, but is not quite sure why yet.  Belle as my alpha is the lead in the protection department and I couldn't ask for a better dog there.  She alerts whenever there is a stranger in the front yard or if there is something that is bothering her, and I don't mean squirrels, birds, etc.  When she barks, I listen and check it out as she rarely barks, and never barks for just the fun of it.  If she is barking, something has her worried..  She also will back a stranger up against a wall in a heartbeat unless I am there and tell her it is ok.  She doesn't attack, she just pins them and they are afraid to move.  Also, people who come to my door (strangers, not friends) always step back off the front porch when they hear her on the otherside of the door.  That is ok by me as I don't worry that someone will easily push their way into the house.  She does quiet and back off with one word from me. Halo is the perfect backing protector dog to Belle as she follows Belles lead to perfection.  Right now Ringo just barks and watches and does what Belle does.  I am certain that they would all three protect me if needed.  Thankfully it has never been needed.  I have never felt more safe than with my three shorthairs.