[Elaine]

"Barking and not acting is perfectly normal."

Yes, for a fearful puppy growing into a fearful aggressive adult dog. My foster puppy is like this and I get after her each and every time she tries it. I will tell her to knock it off in a no nonsense tone and if she continues, I will take her by the collar and lift her up and tell her again, and/or just whack her on the side. I also have everyone and everyone I can get to pet her as often as possible and praise her like crazy when she doesn't do this. She will always have this issue to a degree, but is very manageable now and I don't worry about her growing up aggressive and thinking she can get away with unacceptable behavior and possibly biting someone unprovoked. There is a big difference between this nonsense and growling or barking in a scary situation which they will know the difference as they grow up.

Your dog should be looking to you for guidance at this age for what is acceptable and what isn't, and if you don't step up, your dog will decide for himself that he's right in his aggression and it will get worse.