rethinking "popular" early socialization
---- read this thread regarding socialization
Your pup is 6 months old - a puppy - *if* he has protective instincts, it will begin to appear in another 6 months or so. At this time, it is his job to be a puppy, your job is to protect him from strange off leash dogs.
For safer exposure to other dogs, join a training class or a local club. You want controlled meetings with stable dogs for your pup.