I cant answer your questions with any certainty so I won't even try. I'm sorry. This is just another example of why the majority of us don't usually bother with dog parks. Plus there will come a time that your pup likely won't care for dog parks. Can I ask though, why are you taking him to the dog park? If it's for socialization with other dogs, that's definitely not the way to go about it and you saw first hand why that is.
I'm sorry you had a bad experience and as often times as long as you get your pup out to people watch and socializing with balanced KNOWN dogs in a positive way, I don't think this will have a lasting impact. I would suggest avoiding the dog parks however. All it takes is one instance of your dog having a good time and another dog taking a dislike of him to mess up all your hard work. I speak from experience.
The more people I meet and talk to,the more I love my dogs and their intelligence.
Shasta GSD 5/5/10 CGC
"Dax" Thor z vom Weberhaus 3/18/2013
Zena GSD 6/1/03
Riley GSD/BC 1/10/05-2/1/2013